Mesoplodon.[147]—A much compressed and pointed tooth in each ramus of the mandible, variously situated, but generally at some distance behind the apex (Fig. 86); its point directed upwards, and often somewhat backwards, occasionally developed to a great size. Skull with the region around the nares as in Hyperoödon, except that the nasals are narrow and more sunk between the upper ends of the premaxillæ; like those of Hyperoödon, they are concave in the middle line in front and above. No maxillary tuberosities. Anteorbital notch not very distinct. Rostrum long, narrow, and solid throughout. Mesethmoid in adult age ossified in its entire length, coalescing with the surrounding bones, and showing as a narrow band on the upper surface of the rostrum. Vertebræ: C 7, D 10, L 10 or 11, C 19 or 20; total 46 to 48. Two or three anterior cervicals united, the rest usually free.

Though varying in form, the mandibular teeth of the different members of this genus agree in their essential structure, having a small and pointed enamel-covered crown, composed of true dentine, which, instead of surmounting a root of the ordinary character, is raised upon a solid mass of osteodentine. The continuous growth of this greatly alters the form and general appearance of the organ as age advances, as seen most strikingly in the case of M. layardi, where the long, narrow, flat, strap-like teeth, curving inwards at their extremities, actually meet over the rostrum, and must greatly interfere with the movements of the jaw. In one species (M. grayi) a row of minute, conical, pointed teeth, like those of ordinary Dolphins, 17 to 19 in number, are present even in the adults, on each side of the middle part of the upper jaw, but embedded by their roots only in the gum, and not in bony alveoli. This fact, with the frequent presence of rudimentary teeth in other species of this and the last genus in both upper and lower jaws, suggests the idea that the Ziphioids are derived from ancestral forms which had teeth of normal character in both jaws; the dentition of the living forms having become greatly specialised. The existing species of this genus are widely distributed in both northern and southern hemispheres, but most frequent in the latter. The best established are M. bidens, M. europæus, M. densirostris, M. layardi, M. grayi, and M. hectori; but there is still much to be learned with regard to their distinctive characters and geographical distribution. They were abundant in the Pliocene age, as attested by the frequency with which the most imperishable and easily recognised portion of their structure, the long, cylindrical rostrum of the skull, of more than ivory denseness, is found among the rolled and water-worn fragments of animal remains which compose the well-known “bone-bed” at the base of the Red Crag of Suffolk Several species have been founded upon the evidence of these rostra. Periotic bones of this genus (Fig. 87) are of less common occurrence in the Crag; the figure is given to illustrate the characteristic features of this bone in the present family.

Berardius.[148]—Two moderate-sized, compressed, pointed teeth on each side of the symphysis of the mandible, with their apices directed forwards, the anterior being the larger of the two and close to the apex. Upper ends of the premaxillæ nearly symmetrical, moderately elevated, very slightly expanded, and not curved forward over the nares. Nasals broad, massive, and rounded, of nearly equal size, forming the vertex of the skull, flattened in front, most prominent in the middle line. Anteorbital notch distinct. Rostrum long and narrow. Mesethmoid only partially ossified. Small rugous eminences on the outer edge of the upper surface of the maxillæ at base of rostrum. Vertebræ: C 7, D 10, L 12, C 19; total 48. The three anterior cervicals ankylosed, the rest free and well developed.

The only known species, B. arnuxi, attains the length of 30 feet, and has hitherto only been met with in the seas around New Zealand.

Choneziphius.[149]—The rostral portions of crania from the Antwerp and Suffolk Crags, on the evidence of which this genus has been established, agree with those of Mesoplodon in having the premaxillæ in contact with the intervening bones throughout the length of their inner surfaces, and also in showing only a very small portion of the vomer on the inferior surface; they differ, however, in that the mesethmoid cartilage remains unossified, whereby a fistular vacuity remains. In some species the soldering of the inner surfaces of the premaxillæ is incomplete. The interorbital region of the skull is flat; and there are two pits in the nasal region, of which the right is the larger.

Family Squalodontidæ.

Numerous extinct forms, chiefly known by teeth and fragments of crania, may be provisionally placed here, until more of their osteological characters shall be brought to light. They differ from all existing Cetaceans in having the teeth distinctly differentiated into groups, as in the Archæoceti, the posterior molars being two-rooted. The cranium has, however, none of the distinguishing characteristics of the Zeuglodonts, but essentially resembles that of the Odontoceti, especially in the position of the anterior nares and form of the nasal bones.

Squalodon.[150]—All the forms may be included in this genus, the so-called Rhizoprion not being distinct. Dentition: i ³⁄₃, c ¹⁄₁, simple teeth of the molar series (premolars?) ⁴⁄₄, two-rooted molars ⁷⁄₇ = ¹⁵⁄₁₅; total 60. The double-rooted molars differ from those of Zeuglodon in having the denticulations of the crown confined to the posterior border, or at all events much less developed on the front edge. Very little is known of the structure of these animals beyond the skull and teeth, fragments of which have been found widely distributed throughout the marine Miocene and early Pliocene formations of Europe, especially in the Vienna basin, many parts of France, and the Antwerp and Suffolk Crags. They have also been found in formations of corresponding age in North America and South Australia. A few isolated teeth have been met with in the cave-deposits of Italy, which, if contemporaneous with the beds in which they occur, indicate the survival of the genus into the Pleistocene period.

Family Platanistidæ.

Under this heading may be placed three very singular genera, which, though differing considerably from each other, have several points in common, and do not altogether come under the definition either of the Physeteridæ or the Delphinidæ, especially in the important character of the mode of articulation of the ribs with the dorsal vertebræ, the tubercular and capitular articulations, distinct at the commencement of the series, gradually blending together, as they do in most ordinary mammals. The cervical vertebræ are all free. The lachrymal bone is not distinct from the jugal. The jaws are long and narrow, with numerous teeth in both. The symphysis of the mandible exceeds half the length of the whole ramus. Externally the head is divided from the body by a slightly constricted neck. Pectoral limbs broad and truncated. Dorsal fin small or obsolete. Fluviatile or estuarine in habits. There are three distinct genera, which might almost be made the types of families, but it is probably more convenient to keep them together, only regarding them as representing three subfamilies.

Platanista.[151]—Teeth about ³⁰⁄₃₀ on each side, set near together, rather large, cylindrical, and sharp-pointed in the young; in old animals acquiring a large laterally compressed base, which in the posterior part of the series becomes irregularly divided into roots. As the conical enamel-covered crown wears away, the teeth of the young and old animals have a totally different appearance. The rostrum and dentigerous portion of the mandible are so narrow that the teeth of the two sides are almost in contact. Maxillæ supporting very large, incurved, compressed bony crests, which overarch the nares and base of the rostrum, and almost meet in the middle line above. Orbits very small and eyes rudimentary, without crystalline lens. External respiratory aperture longitudinal, linear. Vertebræ: C 7, D 10, L 9, C 26; total: 52. A small cæcum. No pelvic bones. Dorsal fin represented by a low ridge.

One species, P. gangetica, entirely fluviatile, being extensively distributed throughout nearly the whole of the river systems, not only of the Ganges, but of the Brahmaputra and Indus, ascending as high as there is water enough to swim in, but never passing out to sea. It is quite blind, and feeds on small fish and crustaceans, groping for them with its long snout in the muddy water at the bottom of the rivers. It attains the length of 8 feet.[152]

Inia.[153]—Teeth variable, from 26 to 33 on either side of each jaw; those at the posterior part with a distinct tubercle at the inner side of the base of the crown. Vertebræ: C 7, D 13, L 3, C 18; total 41. Transverse processes of lumbar vertebræ very broad. Sternum short and broad, and consisting of a single segment only. Dorsal fin a mere ridge. The long cylindrical rostrum externally furnished with scattered, stout, and crisp hairs. One species only is known, I. geoffroyensis, about 7 feet in length, inhabiting the upper Amazon and its tributary streams.

Pontoporia.[154]—Teeth 50 to 60 on either side of each jaw, with a cingulum at the base of the crown. Jaws very long and slender. Vertebræ: C 7, D 10, L 5, C 19; total 41. Transverse processes of the lumbar vertebræ extremely broad. Sternum elongated, composed of two segments, with four sternal ribs attached. Dorsal fin rather small, triangular, pointed. External respiratory aperture transverse, crescentic. This genus connects the last two forms with the true Delphinidæ. The only species, P. blainvillei, is one of the smallest members of the whole order, not exceeding 5 feet in length. It has only been met with at the mouth of the Rio de la Plata, near Buenos Ayres, and there is at present no evidence that it ascends into the fresh waters of the river.

Fossil forms.—Remains of a Cetacean from the Pleistocene of South America were referred by Bravard to Pontoporia, but they have been regarded by other writers as indicating a distinct genus, for which the names Palæopontoporia and Pontistes have been proposed. The Upper Tertiary European genera Champsodelphis and Schizodelphis are generally referred to the present family. The former has wide transverse processes to the lumbar vertebræ, as in Inia, while the teeth also resemble those of that genus. In Schizodelphis the form of the rostrum presents a great resemblance to that of the Delphinoid genus Steno, but the symphysis of the mandible is relatively longer. A number of fossil Cetaceans from the Miocene of the United States, such as Priscodelphinus, Lophocetus, Ixacanthus, Rhabdosteus, etc., are referred by Professor E. D. Cope to this family. Agabelus, from the same deposits, is an apparently allied, but toothless type.

Family Delphinidæ.

Teeth usually numerous in both jaws. Pterygoid bones short, thin, each involuted to form with a process of the palate bone the outer wall of the post-palatine air-sinus. Symphysis of mandible short, or moderate, never exceeding one-third of the length of the ramus. Lachrymal bone not distinct from the jugal. The anterior facet on the periotic (Fig. 96) for articulation with the tympanic deeply grooved; and the posterior tympanic surface of the same bone comparatively narrow, with its ridge for articulation with the free border of the tympanic ill-defined, and situated close to one edge. Transverse processes of the dorsal vertebræ gradually transferred from the arches to the bodies of the vertebræ without any sudden break, and becoming posteriorly continuous serially with the transverse processes of the lumbar vertebræ. Anterior ribs attached to the transverse process by the tubercle, and to the body of the vertebra by the head; the latter attachment lost in the posterior ribs. Sternal ribs firmly ossified. External respiratory aperture transverse, crescentic, with the horns of the crescent pointing forwards.

A very large group, closely united in essential characters but presenting great modifications in details. The different types are mostly so connected by intermediate or osculant forms that there are great difficulties in grouping them into natural subfamilies. Even the formation of well-defined genera is by no means satisfactory in all cases. They may, however, be divided, perhaps artificially, into two groups.

Group A.—Head rounded, without distinct rostrum or beak. Rostrum of skull about as long as cranial portion.

Monodon.[155]—Besides some irregular rudimentary teeth, the entire dentition is reduced to a single pair of teeth which lie horizontally in the maxilla, and in the female remain permanently concealed within the alveolus so that this sex is practically toothless, while in the male (see Fig. 90) the right tooth usually remains similarly concealed and abortive, and the left is immensely developed, attaining a length equal to more than half that of the entire animal, projecting horizontally from the head in the form of a cylindrical, or slightly tapering, pointed tusk, without enamel, and with the surface marked by spiral grooves and ridges, running in a sinistral direction. (When, as occasionally happens, both tusks are developed, the spiral grooves have the same direction in each.) Pterygoids very small, not meeting in the middle line, but approximating posteriorly. Vertebræ: C 7, D 11, L 6, C 26; total 50. Cervical region comparatively long, and all the vertebræ distinct, or with irregular unions towards the middle of the series, the atlas and axis being usually free. Manus small, short, and broad; second and third digits nearly equal, fourth slightly shorter. No dorsal fin.

This genus is now represented only by the well-known Narwhal (M. monoceros), in which the horn-like tusk of the male often grows to a length of 7 or 8 feet. In very young animals several small additional teeth, irregular in number and position, are present, but these usually disappear soon after birth.

The head is rather short and rounded; the fore limbs or paddles are small and broad compared with those of most Dolphins; and (as in the Beluga) the median dorsal fin, found in nearly all other members of the group, is wanting or replaced by a low ridge. The general colour of the surface is dark gray above and white below, but variously marbled and spotted with different shades of gray. In the general contour of the body the Narwhal resembles the White Whale or Beluga.

The Narwhal is essentially an Arctic animal, frequenting the icy circumpolar seas, and but rarely seen south of 65° N. lat. Three instances have, however, been recorded of its occurrence on the British coasts, one in the Firth of Forth in 1648, one near Boston in Lincolnshire in 1800, while a third, which entangled itself among the rocks in the Sound of Weesdale, Shetland, in September 1808, is described by Fleming in the Memoirs of the Wernerian Society, vol. i. Like most other Cetaceans, it is gregarious in its habits, being usually met with in “schools” or herds of fifteen or twenty individuals. Its food appears to be various species of cephalopods, small fishes, and crustaceans. The purpose served in the animal’s economy by the wonderfully developed asymmetrical tusk—or “horn,” as it is commonly but erroneously called—is not known. As it is present only in the male sex, no function essential to the well-being of the individual, such as the procuring of sustenance, can be assigned to it, but it must be looked upon as belonging to the same category of organs as the antlers of deer, and perhaps may be applied to similar purposes. Very little is, however, known of the habits of Narwhals. Scoresby describes them as “extremely playful, frequently elevating their horns and crossing them with each other as in fencing.” They have never been known to charge and pierce the bottom of ships with their weapons, as the sword-fish often does. The name “Sea Unicorn,” sometimes applied to the Narwhal, refers to the resemblance of its tusk to the horn represented as projecting from the forehead of the fabled unicorn. The ivory of which the tusk is composed is of very good quality, but, owing to the central cavity, which extends the greater part of its length, is only fitted for the manufacture of objects of small size. The entire tusks are sometimes used for decorative purposes, and are of considerable, though very fluctuating, commercial value.

Delphinapterus.[156]—This genus is closely allied to the last in external form, as well as anatomical structure, differing mainly in the very distinct character of the dentition. Teeth from ⁸⁄₈ to ¹⁰⁄₁₀, occupying the anterior three-fourths of the rostrum and corresponding portion of the mandible, rather small, conical, and pointed when unworn, but usually becoming obliquely truncated, separated by intervals considerably wider than the diameter of the tooth, and implanted obliquely, the crowns inclining forwards, especially in the upper jaw. Skull rather narrow and elongated, depressed. Premaxillæ convex in front of the nares. Rostrum about equal in length to the cranial portion of the skull, triangular, broad at the base, and gradually contracting towards the apex, where it is somewhat curved downwards. Vertebræ: C 7, D 11, L 9, C 23; total 50. Cervical vertebræ free. Manus broad, short, and rounded, all the digits being tolerably well developed, except the first. No dorsal fin, but a low ridge in its place.

One existing species, D. leucas (Fig. 91), the Beluga or White Whale, so called from its pure white colour, about 12 feet long, abundant in the Arctic seas, and extending as far south on the American coast as the river St. Lawrence, which it ascends for a considerable distance. On rare occasions it has been seen on the coast of Scotland.

Remains of a Cetacean from the Lower Pliocene of Tuscany have been referred by Brandt to this genus under the name D. brocchii.

In all the remaining genera of Delphinidæ the cervical region of the vertebral column is very short, and the first two, and usually more, of the vertebræ are firmly united.

Phocæna.[157]—Teeth ²⁵⁄₂₅, small, occupying nearly the whole length of the rostrum, with compressed, spade-shaped crowns, separated from the root by a constricted neck (Fig. 92). Rostrum rather shorter than the cranium proper, broad at the base and tapering towards the apex. Premaxillæ raised into tuberosities in front of the nares. The frontal bones forming a somewhat square, elevated protuberance in the middle line of the skull behind the nares, rising altogether above the flattened nasals. Pterygoids very small, and widely separated in the middle line. Symphysis of mandible very short. Vertebræ: C 7, D 13, L 14, C 31; total 65 (subject to slight individual variations). First to sixth cervical vertebræ, and sometimes the seventh also, coalesced. Manus of moderate size, oval, slightly falcate; second and third digits nearly equal in length; fourth and fifth well developed, but shorter. Dorsal fin near the middle of the back, triangular; its height considerably less than the length of the base; its anterior edge frequently furnished with one or more rows of conical horny tubercles.

The common Porpoise (Fig. 93), P. communis, is the best known of British Cetaceans. The word Porpoise (sometimes spelled Porpus and Porpesse) is apparently derived from the French porc and poisson, or the Italian porco and pesce, and thus corresponds with some of the English vernacular appellations, “hog-fish,” “sea-hog,” “herring-hog,” and the German Meerschwein, whence the usual modern French name of the animal, marsouin. “Porpoise” is commonly used by sailors to designate all the smaller Cetaceans, especially those numerous species which naturalists call “Dolphins”; but in scientific language it is restricted to the genus Phocæna of Cuvier, of which the Porpoise of the British seas, Phocæna communis, Cuvier (Delphinus phocæna, Linnæus), is the type.

The Common Porpoise, when full grown, attains a length of 5 feet or a little more. The dimensions of an adult female specimen from the English Channel were as follows:—length in straight line from nose to median notch between the flukes of the tail, 62½ inches; from the nose to the anterior edge of the dorsal fin, 29 inches; height of dorsal fin, 4½ inches; length of base of dorsal fin, 8 inches; length of pectoral fin, 9¼ inches; breadth of pectoral fin, 3½ inches; breadth of tail flukes, 13 inches. The under jaw projects about half an inch beyond the upper one. The aperture of the mouth is tolerably wide, and is bounded by stiff immobile lips, and curves slightly upwards at the hinder end. The eye is small, and the external ear represented by a minute aperture in the skin, scarcely larger than would be made by the puncture of a pin, situated about 2 inches behind the eye. The pectoral fins are of moderate size, and slightly falcate. The upper parts are dark gray, or nearly black, according to the light in which they are viewed, and the state of moisture or otherwise of the skin; the under parts are pure white. The line of demarcation between these colours is not distinct (washes or splashes of gray encroaching upon the white on the sides), and varies somewhat in different individuals. Usually it passes from the throat (the anterior part of which, with the whole of the under jaw, is dark) above the origin of the pectoral fin, along the middle of the flank, and descends again to the middle line before reaching the tail. Both sides of the pectoral and caudal fins are black.

The Porpoise is sociable and gregarious in its habits, being usually seen in small herds, and frequenting coasts, bays, and estuaries rather than the open ocean. It is the commonest Cetacean in the seas around the British Isles, and not unfrequently ascends the river Thames, having been seen as high up as Richmond; it has also been observed in the Seine at Neuilly, near Paris. It frequents the Scandinavian coasts, entering the Baltic in the summer; and is found as far north as Baffin’s Bay, and as far west as the coasts of the United States. Southward its range is more limited than that of the Common Dolphin, as, though very common on the Atlantic coasts of France, it rarely enters the Mediterranean.

It feeds on fish, such as mackerel, pilchards, and herrings, of which it devours large quantities, and, following the shoals, is often caught by fishermen in the nets along with its prey. In former times it was a common and esteemed article of food in England and in France, but is now rarely if ever eaten, being commercially valuable when caught only for the oil obtained from its blubber. Its skin is sometimes used for leather and boot-thongs, but the so-called “porpoise hides” are generally obtained from the Beluga.

A closely similar if not identical species from the American coast of the North Pacific has been described under the name of Phocæna vomerina, and another from the mouth of the Rio de la Plata as P. spinipennis.

The stomach of the Porpoise (Fig. 94) may be taken as a typical example of this organ in the Cetacea. The first and by far the largest compartment (b) may be regarded as a kind of crop, or dilatation of the large œsophagus (a). It is lined by a thick white epithelium, which ceases abruptly at the entrance into the next cavity. It corresponds to the cardiac compartment of the stomach in the Ungulates and certain Rodents; but, although its walls do not appear to contain peptic glands, its contents undergo partial digestion—probably caused by the regurgitation into it of the secretions of the second, or true digestive compartment (c). This, which is much smaller than the first, has very thick walls, the mucous membrane being filled with numerous tubular glands. The surface of this membrane is smooth and soft, being thrown into numerous folds, which in this genus are arranged in a very peculiar and characteristic manner, so as to form a series of prominent longitudinal ridges, each of which sends off short lateral ridges at right angles to itself, which interdigitate with those proceeding from the next longitudinal ridge. The remainder of the stomach (d to f) may be compared to the pyloric antrum of the stomach of ordinary mammals. It is elongated, cylindrical, and intestiniform, with a smooth lining membrane, sharply bent upon itself, and terminating in a very small circular pyloric aperture (f). In the Porpoise the commencement of this cavity is constricted off from the remainder, so as to form a small globular sac. In most Dolphins (as Tursiops, Globicephalus, and Grampus) there are two such small sacs of very similar size and form, communicating by circular pylorus-like apertures; and in Hyperoödon the whole compartment is divided by a series of constrictions into as many as seven separate cavities, which have been regarded as distinct stomachs. Immediately beyond the pylorus the duodenum has a globular dilatation, as in the camels and some other Ungulates, into the lower end of which the biliary duct (h) enters.

An allied species, differing mainly in the absence of dorsal fin, and in the teeth (with the same form of crown) being fewer in number and of larger size, called Delphinus phacænoides by Cuvier, D. melas by Schlegel, forms the type of Gray’s genus Neomeris.[158] It is rather smaller than the Common Porpoise, and almost entirely black in colour. Common off the coast of Bombay, it has been met with in other parts of the Indian Ocean, and near Japan. The British Museum recently received a specimen taken in the Chinese river Yang-tse-kiang nearly a thousand miles from the sea, which only differs from others from India in wanting a patch of small horny tubercles on the back. As such tubercles are present or absent in otherwise similar individuals of P. communis, it is doubtful whether they can be regarded as constituting a specific character.

Cephalorhynchus.[159]—Rostrum as long and sometimes slightly longer than the cranial portion of the skull. Pterygoids widely separated from one another. Teeth small (less than 3 mm. in diameter), ²⁵⁄₂₅ to ³⁰⁄₃₀. Vertebræ: C 7, D 13, L 15, C 30; total 65. Dorsal fin low, obtusely triangular or rounded. Pectoral fins rather small, narrow, and ovate. Typified by C. heavisidei, from the southern seas. C. eutropia is a very distinct form from the same seas, known only by the skull, and referred provisionally to this genus.

Orcella.[160]—Teeth ¹²⁄₁₂ to ¹⁴⁄₁₄, small, conical, pointed, rather closely set, and occupying nearly the whole length of the rostrum. Skull subglobular, high. Rostrum nearly equal in length to the cranial portion of the skull, tapering. Pterygoids widely separated from one another. Manus of moderate size, not elongated, but somewhat pointed. All the bones of the digits broader than long, except the proximal phalanges of the index and third fingers. Dorsal fin rather small, placed behind the middle of the body. Two species, both of small size—O. brevirostris, from the Bay of Bengal, and O. fluminalis, from the Irawadi river, from 300 to 900 miles from the sea. Our present knowledge of the anatomy, geographical distribution, and habits of these interesting Cetaceans is almost entirely due to the researches of Dr. J. Anderson.[161]

Orca.[162]—Teeth about ¹²⁄₁₂, occupying nearly the whole length of the rostrum, very large and stout, with conical recurved crowns, and large roots, expanded laterally and flattened, or rather hollowed, on the anterior and posterior surfaces. Rostrum about equal in length to the cranial part of the skull, broad and flattened above, rounded in front; premaxillæ broad and rather concave in front of the nares, contracted at the middle of the rostrum, and expanding again towards the apex. Pterygoids of normal form, but not quite meeting in the middle line. Vertebræ: C 7, D 11-12, L 10, C 23; total 51 or 52. Bodies of the first and second and sometimes the third cervical vertebræ united; the rest free. Pectoral fin very large, ovate, nearly as broad as long. All the phalanges and metacarpals broader than long. General form of body robust. Dorsal fin near the middle of the back, very high and pointed. Anterior part of the head broad and depressed.

The animals composing this genus are met with in almost all seas from Greenland to Tasmania, but the number of species is still uncertain, and possibly they may be all reduced to one. They are readily known, when swimming in the water, by the high, erect, falcate dorsal fin, whence their common German name of Schwertfisch (Sword-fish). By English sailors they are generally known as “Grampuses” or “Killers.” They are distinguished from all their allies by their great strength and ferocity, being the only Cetaceans which habitually prey on warm-blooded animals, for, though fish form part of their food, they also attack and devour Seals, and various species of their own order, not only the smaller Porpoises and Dolphins, but even full-sized Whales, which last they combine in packs to hunt down and destroy, as Wolves do the larger Ruminants.

Orca citoniensis, of the Italian Pliocene, was of smaller size than the existing Killer. Teeth and periotic bones from the Suffolk Crag not improbably belong to the same species.

Pseudorca.[163]—Teeth about ¹⁰⁄₁₀. Cranial and dental characters generally like those of Orca, except that the roots of the teeth are cylindrical. Vertebræ: C 7, D 10, L 9, C 24; total 50. First to sixth or seventh cervical vertebræ united. Bodies of the lumbar vertebræ distinguished from those of the preceding genera by being more elongated, the length being to the width as 3 to 2. Pectoral fin of moderate size, narrow, and pointed. Dorsal fin situated near the middle of the back, of moderate size, falcate. Head in front of the blowhole high, and compressed anteriorly, the snout truncated.

This genus was first known by the discovery of a skull in a subfossil state in a fen in Lincolnshire, named by Sir R. Owen Phocæna crassidens. Animals of apparently the same species were afterwards met with in small herds on the Danish coast, and fully described by Reinhardt. Others subsequently received from Tasmania were supposed at first to indicate a different species, but comparison of a larger series of specimens from these extremely distant localities fails to establish any characteristic difference, and indicates an immense range of distribution for a species apparently so rare. The length of this Cetacean is about 14 feet, and its colour entirely black.

Globicephalus.[164]—Teeth ⁸⁻¹²⁄₈₋₁₂, confined to the anterior half of the rostrum and corresponding part of the mandible, small, conical, curved, sharp-pointed when unworn, sometimes deciduous in old age. Skull broad and depressed. Rostrum and cranial portion about equal in length. Upper surface of rostrum broad and flat. Premaxillæ strongly concave in front of the nares, as wide at the middle of the rostrum as at the base, or wider, and very nearly or completely concealing the maxillæ in the anterior half of this region. Pterygoids of normal form, meeting, or very nearly so, in the middle line. Vertebræ: C 7, D 11, L 12-14, C 28-29; total 58 or 59. Bodies of the anterior five or six cervical vertebræ united. Length of the bodies of the lumbar and anterior caudal vertebræ about equal to their width. Pectoral limb very long and narrow, the second digit the longest, and having as many as 12 or 13 phalanges, the third shorter (with 9 phalanges), the first, fourth, and fifth very short. Fore part of the head very round, in consequence of the great development of a cushion of fat, placed on the rostrum of the skull in front of the blowhole. Dorsal fin low and triangular, the length of its base considerably exceeding its vertical height.

The type of this well-marked genus is G. melas, the Pilot Whale, Ca’ing Whale, or Grindhval of the Faroe islanders, which attains the length of 20 feet, and is of nearly uniform black colour, except the middle of the under surface, which is lighter. These animals are extremely gregarious, and, unlike the Killers, are mild and inoffensive in disposition, feeding principally on cephalopods. Their eminently sociable character constantly leads to their destruction, since when attacked they instinctively rush together and blindly follow the leaders of the herd. When they are seen in the neighbourhood of land, the fishermen endeavour to get to seaward of them in their boats, and with shouting and firing of guns to drive them into a bay or fjord, pursuing them until they run themselves on shore in their alarm. In this way many hundreds at a time are frequently driven ashore and killed, when a herd enters one of the bays or fjords of the Faroe Islands or north of Scotland. Animals of this well-marked genus are found in nearly all seas, and their specific distinctions are not yet made out. Specimens from the Australian coasts, where they are generally called “Black-fish,” are quite indistinguishable, either by external or osteological characters, from those of the North Atlantic.

Teeth, periotic (Fig. 96) and tympanic bones from the Suffolk Crag, described as G. uncidens, indicate a form apparently closely allied to the existing species. The periotic is figured in order to illustrate the distinctive characters of that bone in the Delphinidæ.

Grampus.[165]—Teeth none in the upper jaw; in the mandible few (3 to 7 on each side), and confined to the region of the symphysis. Vertebræ: C 7, D 12, L 19, C 30; total 68. General external characters much as in Globicephalus, but the fore part of the head less rounded, and the pectoral fin less elongated.

But one species, G. griseus, is certainly known, about 13 feet long, and remarkable for its great variability of colour. It has been found, though rarely, in the North Atlantic and Mediterranean. A skull from the Cape of Good Hope, which differs slightly from that of the above, has been described under the name of G. richardsoni.

Feresia.[166]—This genus, known at present only by two skulls, may be provisionally placed here. These appear to indicate a form connecting Globicephalus, Grampus, and Lagenorhynchus. From the latter they differ chiefly in the smaller number (about ¹²⁄₁₂) and much larger size (6-7 mm. in diameter at base of crown) of the teeth.

Lagenorhynchus.[167]—Rostrum scarcely exceeding the length of the cranium, broad at the base and gradually tapering towards the apex, depressed. Pterygoids normal, meeting in the middle line. Teeth small (not exceeding 4 mm. in diameter), ²³⁄₂₃ to ³³⁄₃₃. Vertebræ very numerous, 80 to 90. Spines and transverse processes of the lumbar vertebræ very long and slender; centra short. Externally, head with a short but not very distinct beak. Two species, L. albirostris and L. acutus, are occasionally captured on the British coasts. Other species occur elsewhere.

Group B.—Head with distinctly elongated rostrum, or beak, generally marked off from the prenarial adipose elevation by a V-shaped groove. Rostrum of skull considerably longer than the cranial portion. Atlas and axis firmly united; all the other cervical vertebræ free.

If we add to it the above-mentioned genus, Lagenorhynchus, this group will include all the true Dolphins, Bottle-noses, or, as they are more commonly called by seafaring people, “Porpoises,” which are found in considerable abundance in all seas, some species being habitually inhabitants of large rivers, as the Amazon. They are all among the smaller members of the order, none exceeding 10 feet in length. Their food is chiefly fish, for the capture of which their long narrow beaks, armed with numerous sharp-pointed teeth, are well adapted, but some appear also to devour crustaceans and molluscs. They are mostly gregarious, and the agility and grace of their movements in the water are constant themes of admiration to the spectators of the scene when a “school of Porpoises” is observed playing round the bows of a vessel at sea.

Delphinus.[168]—Teeth very numerous in both jaws, ⁴⁰⁄₄₀ to ⁶⁰⁄₆₀, occupying nearly the whole length of the rostrum, small, close-set, conical, pointed, slightly curved. Rostrum elongated, usually about double the length of the cranial portion of the skull. Pterygoids of normal form, meeting in the middle line throughout their length. Palate with deep lateral grooves. Vertebræ 73 to 75. Pectoral fin of moderate size, narrow, pointed, somewhat falcate. Second and third digits well developed; the rest rudimental.

The type of the genus is the Common Dolphin of the Mediterranean (D. delphis, Fig. 97), also found in the Atlantic, and of which a closely allied if not identical form is met with in the Australian seas (D. forsteri) and in the North Pacific (D. bairdi). Other species are D. janira, D. major, etc.