C. mænas (M. J. Rathbun), Carcinus mænas (Leach), the green crab. This is one of the most common species on the Atlantic coast from Cape Cod to New Jersey, and is very abundant in Vineyard Sound, Buzzard's Bay, and Long Island Sound. It is found between tide-marks, frequently well up on the beach, hiding under loose stones, also in tide-pools and in holes and cavernous places on the shore. It is from one and a half to two inches long, and a little more in breadth. It has five acute teeth on each side of the anterior part of the carapace. Its color is green, spotted with yellow, making it quite conspicuous. The surface of the carapace and limbs is more or less granulated. The posterior feet are flattened to form swimming-paddles. It is a very lively creature and has reckless audacity when brought to bay, which justifies its specific name (which implies frenzy). The French call it crabe enragé. [pg275]
Genus Callinectes
C. sapidus (Mary J. Rathbun), C. hastatus (Stimpson), the blue crab. This is the common edible crab of the Atlantic coast. It is known at the North as the "blue crab," and at the South as the "sea-crab." It is found from Cape Cod to Florida, and after the lobster is the crustacean which has the greatest commercial value, being taken in immense quantities for the markets, not only when the shell is hard, but immediately after moulting, before the new shell has hardened, when it is known as the "soft-shelled crab." It inhabits muddy shores, and is common in bays and at the mouths of estuaries. The carapace is about twice as broad as it is long, and has a long, sharp spine on each side which projects outward. This is a distinguishing feature. There are eight short spines on each side between the long spines and the eyes; then come recesses for the eyes, and between the eyes are four unequal teeth and a small spine underneath. The chelæ are large and somewhat unequal in size; then come three pairs of simple feet and a fifth pair, which are flattened, forming swimming-organs. The margins of the carapace and abdomen are fringed with fine hairs, as are also most of the joints of the limbs. The upper surface of the body and claws is dark green in color, the lower surface is dingy white, the feet blue, and the tips of the spines reddish. The body is compressed, the carapace being moderately convex above, and is covered with minute granulations, which are more numerous over some portions than over others. The abdomen of the female is very broad and fills the entire space between the bases of the posterior pair of feet. During the spawning season it is so charged with eggs that often it projects out almost at right angles with the carapace. The [pg276] crabs of this species are very active and can swim rapidly. They also have the habit of pushing themselves backward into the mud for concealment. They are predaceous and pugnacious, and have great strength in their claws, which they use with dexterity. They not only fight their own kind, but show a bold front to all enemies, including man. The average size is six inches across the carapace.
Genus Ovalipes
O. ocellatus (Rathbun), Platyonichus ocellatus (Latreille), the lady-crab or sand-crab. A species common on sandy shores from Cape Cod to Florida. It is found among the loose sands at low-water mark, even on the most exposed beaches, and also is abundant on sandy bottoms offshore. At low-water mark it buries itself up to the eyes and antennæ in the sand, where it watches for prey and foes, and quickly disappears beneath the sand when danger approaches. It possesses the power of burrowing in common with other marine animals which inhabit exposed beaches of loose sand. By burying itself deep in the sand it is protected from the action of the breakers. This species is easily distinguished by the color and shape of its carapace, taken in connection with its posterior swimming-feet. The body is nearly as long as it is broad, with five prominent spines on each side. The front margin is indented on each side of a three-spined rostrum, to form cavities for the eyes. The first limbs are large and have claws; the posterior ones are flattened into swimming-feet, and the intermediate three pairs are simple in structure, ending in points. In color it is white, covered with spotted rings of red and purple. [pg277]
WALKING CRABS
Family CANCROIDÆ
Genus Cancer
C. irroratus, the rock-crab. This is the common crab of the New England coast. It ranges from Labrador to South Carolina, but is rare south of New Jersey. It is found on sandy as well as on rocky shores at and below low-water mark and also between tide-marks, hiding among rocks, nearly buried in sand or gravel, and in tide-pools, where sometimes amusing combats between the males may be seen. The carapace is suboval, one third broader than long, the breadth being often from three to four inches. The surface is granulated but smooth; the color is yellowish, closely dotted with brown. The eyes are on short stalks in deep, circular holes, and between the eyes are small teeth. There are nine blunt teeth along each side of the front edge of the carapace. The first pair of legs are short and stout, and terminate in claws. The four posterior pairs are slender and end in pointed tips. This is an edible crab, and it is devoured by the larger fishes, but does not—although there seems to be no reason for it—share to any extent a place in the markets with the blue crab, Callinectes sapidus.
C. borealis, the Jonah crab. This crab resembles, and is frequently taken for, C. irroratus. It is larger than the latter in full growth, and is heavier and more massive. The carapace and claws are rougher, the granules being irregular in size. The legs are proportionately shorter and heavier. The teeth on the anterior margins are rounded in front, but the posterior ones are sharply pointed. In color [pg278] it is brick-red above and yellowish beneath. It inhabits rocky shores only and is found at low tide on the surface of the rocks, where it is exposed to the action of the waves and also to the attacks of birds of prey, which feed upon it, while C. irroratus, concealed under the rocks in the same locality, escapes their depredations. This species is supplied to the Newport market, where it is considered preferable to the blue crab. Its range is from the eastern end of Long Island to Nova Scotia.
C. magister. This species inhabits the Pacific coast and ranges from Alaska to Lower California. The adult male is from seven to nine inches broad and from four to five inches long. The anterior margin of the carapace is an almost regular elliptical curve with nine small teeth on each side. At the end of the curve a large, pointed tooth projects directly outward, and from this the carapace slopes abruptly backward, giving a narrow posterior end. The surface of the carapace is undulated and covered with papillæ, and is light reddish-brown, shading to lighter color in the back. The color of the legs and under surface of the animal is yellowish. The claws are toothed above and ribbed at the sides. It inhabits sandy bottoms below tide-mark and is the largest and most important edible crab of the western coast.
C. productus, the red crab. This species, like the preceding one, is of large size and inhabits the western coast from Alaska to the Gulf of California. The carapace is four and a half inches in length, from five to seven in breadth, and somewhat elliptical in outline. The teeth on the anterior margin are distinctly separate in the adult, but in the young appear as wrinklings of the edge of the carapace. The posterior margins are concave. In color the animal is dark red above and yellowish beneath in the adults, but variable in the young, sometimes being yellow spotted with red, or banded with red and yellow. It inhabits rocky shores. This is an edible crab, but is not taken for the markets, C. magister supplying all demands. [pg279]
C. antennarius, the rock-crab of the Pacific coast. This species of the California coast inhabits rocky bottoms below low-water mark. The carapace is three and a half inches long by five or six inches wide, and dark purplish-brown in color. The chelæ are marbled with purplish spots and are nearly smooth. The distinguishing features of this crab are its large and hairy antennæ, the hirsute margins of its abdomen and walking-feet, and the numerous hairs on the under side of its body.
Genus Menippe
M. mercenaria, the stone-crab. This species lives in deep holes in the mud along the borders of creeks and estuaries, and also in crevices between fragments of rock, in stone-heaps and other debris, and is found from South Carolina to Texas. These crabs are edible, and in some localities are hunted for food, one manner of capturing them being to thrust the hand and arm into their holes and drag them out, an operation attended with danger to the inexperienced hunter, who is likely to be badly pinched. They are withdrawn with difficulty, as they offer a strong resistance, bracing themselves with their claws against the sides of their holes, and often hold so firmly to the rocks that they are torn [pg281] apart. They are also taken by a hooked iron which is thrust into the hole; the crab seizes it and is then suddenly jerked from its hole. The adult measures about three by four and a half inches, and the body is from one inch to two inches thick. One of the chelæ is larger than the other, and both are proportionately enormously large, and are tipped with black. The terminal joints of the other four pairs of legs are thickly fringed with hairs and end in points which seem like nails.
Former Genus Panopeus
Eupanopeus herbstii, Eurypanopeus depressus, Neopanopeus texana, Rhithropanopeus harrisii (Mary J. Rathbun). These four species, formerly all called Panopeus, are small crabs which live in the mud and are commonly known as mud-crabs. They are abundant under stones in muddy places, and occur on the Atlantic coast from Massachusetts Bay to Florida, though they are not commonly met with north of New Jersey. Eupanopeus herbstii is the largest one of the group, some of the Southern ones measuring two inches across. It is found living in mud at low-water mark, or burrowing in banks near high-tide mark. It is dark olive-brown, the claws broadly tipped with black. Eurypanopeus depressus is flattened above, and is smaller than Neopanopeus texana, which is somewhat convex above. The last two are commonly found together and have similar habits. Rhithropanopeus harrisii lives near high-water mark and also in salt-marshes, and is comparatively rare. The claws lack the dark tips of E. herbstii, and a distinct groove follows the edge of the carapace.
Family GRAPSIDÆ
Genus Hemigrapsus
H. nudus (Mary J. Rathbun), Heterograpsus nudus (Stimpson); H. oregonensis (Mary J. Rathbun), Heterograpsus oregonensis (Stimpson). These two species, commonly called respectively the purple shore-crab and the yellow shore-crab, are the most abundant species of the California coast. Hundreds may be found congregated under a single rock. They range from Sitka to Lower California. H. oregonensis literally swarms in sloughs of salt or brackish water, and hundreds of uplifted threatening claws confront the intruder who ventures on these mud-flats when the tide is out. This species, the yellow shore-crab, has a nearly square body. The anterior half of the side margins has two rather deep indentations, [pg282] making two spine-like projections which bend forward. The four posterior pairs of legs are more or less hairy; the chelæ are rather large in proportion. The male is about one inch across and the female is one third less in size. The general color is yellow. H. nudus is found in the same localities, and differs from H. oregonensis in being purple in color, with mottled claws, and in having the denticulations less pronounced and the walking-feet devoid of hairs. It is also a little larger. (Plate LXIII.)
Genus Pacygrapsus
P. crassipes. A species very common on the California coast south of San Francisco. This crab is similar in general features to the purple and yellow ones described above, but is considerably larger, and the carapace is banded with color.
Family OCYPODIDÆ
Genus Ocypoda
O. arenaria, the sand- or ghost-crab. The name Ocypoda means "swift-footed," and, as it implies, this species is especially noted for its rapidity of movement. These crabs are the opposite of the strong-armed, thick-shelled, slow-moving Cancroidæ. An instance is told of a collector having great difficulty to keep up at full run with one which he chased for a considerable distance over the sand. They are also dexterous in burrowing, and live in holes, often three feet deep, dug perpendicularly into the sand. They wander far from their burrows when the tide is out, and every little while raise their stalked eyes and stand on tiptoe to look about. If alarmed, they run with great rapidity to the nearest burrow, or, if danger is close, press themselves on the sand until an attempt is made to touch them, when they again dart away rapidly, and in running hold their bodies high, and double and dodge so that it is difficult to catch them. Ocypoda is colored almost exactly like the sand, and this mimicry, together with its fleetness, makes it interesting to note and difficult to capture. It inhabits sandy beaches above tide-mark from Long Island to Brazil, and subsists largely upon the beach-fleas, which inhabit the same localities. It springs upon them, very much as a cat catches a mouse. The carapace of this species is almost square in outline, and on the anterior corners ends in a spine. A small portion of the carapace folds down like a band between the eyes. On each side of this band, and extending across the front, are large grooves for the eye-stalks. The body is about an inch thick; the first joints of the chelæ are toothed; one chela is a little longer than the other, and both are coarsely granulated. The other four pairs of legs are thickly fringed with hairs. (Plate LXIII.)
| PLATE LXIII. | |
|---|---|
| Hemigrapsus nudus. | Hyas araneus. |
| Ocypoda arenaria. | Pugettia gracilis. |
| Libinia dubia. | Pitho aculeata. |
Genus Uca
U. minax (Gelasimus minax), U. pugnax (Gelasimus pugnax), U. pugilator (Gelasimus pugilator), the fiddler-crabs. These species [pg283] of fiddler-crabs occur on the Atlantic coast. They congregate in immense numbers, and excavate their holes in convenient localities above the reach of the tides—on salt-marshes, far up the estuaries, and along the mouths of rivers, even where the water is quite fresh. The males have one claw very largely developed; the other chela is small. The former is likened to a fiddle, the latter to a bow, and this, together with the waving motion of the large claw, gives them their popular name. This comparatively enormous claw is a distinguishing feature by which they are easily recognized without other description. The female has claws of small and equal size. These crabs burrow holes in the mud or sand half an inch to two inches in diameter and a foot or more in depth. The upper part is nearly perpendicular, becoming horizontal below, with a chamber at the end. One species, U. minax, constructs an archway over the mouth of its burrow, in which it sits and surveys the surroundings, but quickly retreats when danger approaches. The crab makes its burrow by scraping up the mud or sand and forming it into pellets, which it carries under the three anterior walking-feet on the under side, using the legs on the side moving forward, and the fourth one on the other side, to climb out of the hole. After peering cautiously about, the crab emerges, and carries its load four or five feet away before dropping it; then again looks about before quickly running back; and, finally, turning its stalked eyes, looks in all directions and suddenly disappears, soon to return with another load. The burrows cover considerable areas, and the crabs are so abundant that the marshes and shores sometimes seem to be alive with them. When alarmed, they lift the large claw and run sideways, after the manner of all crabs, to their holes, and, as many are likely to retreat into the most convenient one, the owner often finds his burrow occupied by other tenants, whom he unceremoniously proceeds to pull out. U. minax ranges from southern New England to Florida, and lives on salt-marshes farther away from the sea than the others, and often where the water is quite fresh. It is larger than the other species, and can be distinguished by a red patch at the joints of the legs. It is a vegetarian in diet, living on small algæ. This is the species which constructs a little observation-house over the mouth of its burrow. It can live out of water, and without food, for several days. U. pugilator lives on sandy and muddy flats and beaches near high-water mark, where the sand is compact and somewhat sheltered, and ranges from Cape Cod to Florida. This species, like U. minax, is a vegetarian. U. pugnax is exceedingly abundant on muddy banks and ditches of salt-marshes, the banks being sometimes completely honeycombed and undermined by them. It ranges from Cape Cod to Florida. [pg284]
Family MAIIDÆ
The members of this family are known as "spider-crabs." Their bodies are thick and more or less round in form, narrowing in front to a long, beak-like projection. The surface is generally rough and irregular, having tubercles, spines, prickles, and hairs. The legs are long. These crabs are often covered with seaweeds, hydroids, and other organisms, which they gather with their long and flexible chelipeds and place upon their backs, presumably to conceal themselves from their enemies. They seem to select, instinctively or with reason, such things as will bear transplanting, sometimes using sponges and polyps which are not destroyed by being torn apart, and they also select their dress with reference to its masking uses. A Hyas covered with bright-colored algæ was seen to remove them and replace them with sponges, when transferred to the locality of the latter, where the former did not grow. The animal takes in his claw the object he has gathered, and first holds it to his mouth, where it is moistened with a secretion of mucus or cement, and then places it on his back. If it does not hold, the operation is repeated, often several times, a new spot on the shell being selected each time. It has also been found that the coats of these crabs are covered with hairs which are differently arranged in different genera, some being hooked, others serrated, etc., and that these aid in holding the transplanted organisms in place. The crab is sometimes so covered with these growths as to be entirely concealed beneath them. It is a sluggish animal, and inhabits shallow water along the whole of the Atlantic and Pacific coasts.
Genus Libinia
L. dubia, L. emarginata. These two species inhabit the Atlantic coast, and are found on muddy shores and flats, among decaying seaweed, in eel-grass, and even beneath the surface of the mud. They are covered with hairs, and sometimes have planted on their backs algæ, hydroids, and even barnacles. The legs of L. emarginata often spread a foot or more. The males are much larger than the females. The species ranges from Maine to Florida. L. dubia does not extend north of Cape Cod. It is found more commonly than L. emarginata in very shallow water [pg285] near shore. It is not so thickly covered with spines, and has a longer rostrum, which is also more deeply divided at the end. (Plate LXIII.)
Genus Hyas
H. coarctatus, the toad-crab. This species of spider-crab is found from Greenland to New Jersey, in shallow as well as in deep water. Its body resembles strongly, both in form and size, that of a toad, hence its common name. It forms an important part of the food of the cod.
H. lyratus. A toad-crab of the Pacific coast, ranging from Bering Sea to Puget Sound; named from the lyre-shape of its carapace.
H. araneus. A species which especially resembles a toad in its form. Found off the northern New England coast. (Plate LXIII.)
Genus Loxorhynchus
L. crispatus, the sheep-crab. This crab occurs on the coast of southern California. The body is thick and about three inches across the widest portion, and tapers to a long, prominent rostrum. It is covered with long tubercles and spines and with short, bristly hairs; the legs are long, the chelipeds stretching fully two feet.
Genus Pugettia
P. gracilis. A small spider-crab found on the Pacific coast from Alaska to Puget Sound. Its body is one half of an inch wide and [pg286] one inch long, with prominent spines on the sides of the carapace, which narrows in front into a long beak ending in two spines. It is red and green above, red beneath. (Plate LXIII.)
Genus Sternorhynchus
S. sagittarius. This is one of the most delicately formed of the spider-crabs. The body has narrow longitudinal stripes of light and dark color. It lives offshore from Cape Hatteras southward.
Genus Epialtus
E. productus, the kelp-crab. This crab inhabits the coasts of California and Oregon, and is found among seaweeds on rocks just below low-water mark. The carapace is smooth, is quadrate in form, is about two inches long and broad, has two spines on each side, and has a prominent denticulated rostrum. This is the most common spider-crab of the Pacific (California) coast. It is olive-green, thus simulating in color the kelp among which it lives. (See page 285.)
Genus Pitho
P. aculeata. The carapace has six spines on each side, the middle two being sometimes partly united; the general outline is pentagonal; the length about one inch. Quite common on the Florida coast. (Plate LXIII.)
Genus Lambrus
L. pourtalesii, the long-armed spider-crab. The carapace is broader than it is long and has three elevations all covered with spines. The general surface is pitted and granulated; the rostrum points downward; the chelipeds are very long, the margins armed with spines; the breadth of the carapace is about one and a half inches; and the length of the chelipeds is about three and a half inches. Its range is from Cape Cod to Florida, and it lives among the rocks. (Plate LXIV.) [pg287]
Family CALAPPIDÆ
Genus Calappa
C. flamma, the box-crab. This singular animal lives on sandy and muddy bottoms offshore, from North Carolina southward. The carapace is broad and straight on the posterior side, and is curved on the anterior side, narrowing to the front. The posterior side has prominent denticulations. The body is one and a half inches thick, about four to five inches wide, and two to three inches long. The chelæ are large, broad, and flattened, and are so arranged that when flexed they fit closely together across the front. When folded, and the small legs are withdrawn under the carapace, the animal is shut up as if in a box, and resembles a shell. When in danger it closes its doors, as it were, and abandons itself to the waves, which often carry it ashore. The crested claws resemble the head of a cock. (Plate LXIV.)
Family PINNOTHERIIDÆ
Genus Pinnotheres
P. ostreum, the oyster-crab. The female of this species lives in the gill-cavity of the oyster, and is particularly abundant in oysters from the Chesapeake. The males are seldom seen, and rarely occur in the oyster, but swim freely about. They are smaller than the female, have a firmer shell, and are dark brown above, with a dorsal stripe and two conspicuous spots. The under side of the legs is whitish. The female is commensal, at least in the adult form, and its thin, whitish, transparent carapace is tinged with pink. The species P. maculatum lives in Mytilus edulis (mussel) and in the smooth scallop, Pecten magellanicus. The oyster-crab is a true messmate, and its presence in the oyster may be advantageous in helping to provide food for its host. This crab, like the rest, holds its eggs in the posterior feet until hatched, when the larvæ leave the parent and swim about for a while. The females, at the megalops stage, enter oysters—sometimes two enter the same oyster, but seldom more than one; there it remains permanently, growing to the size of an inch or more in diameter, and becomes a degenerate. The eyes become smaller; the shell never hardens, like its allies which live in open water; its limbs and chelæ are weak; and it has no pugnacity, the protection afforded by the oyster doing away with the need for the common protective features of its kind. Pinnixa cylindrica, a related species, lives in the tubes of large annelid worms as a commensal. [pg288]
ORDER STOMATOPODA
Genus Squilla
S. empusa. This animal suggests somewhat the lobster, though very unlike it. The carapace is much smaller and softer, and leaves the last three segments of the thorax uncovered. The abdomen is larger and longer in proportion, while the legs and organs are quite different. The whole body is depressed, instead of laterally compressed. It measures from eight to ten inches in length and two inches in breadth. Instead of chelæ, the last joint of the great claw has six sharp curved spines, which fit into sockets in a groove on the second joint. By this singular organ they hold their prey securely. The abdominal feet carry the gills. The antennal scales are oblong and fringed with hair. The antennules terminate in three flagella. The caudal appendages and telson are long, strong, and armed with spines. This animal lives in burrows in the mud below low-water mark, forming large, irregular holes, but is frequently washed ashore. In color it is pale yellowish-green, each segment being bordered with darker green and edged with yellow. It is found from Cape Cod to Florida.
ORDER CUMACEA
Genus Diastylis
D. quadrispinosus. Among the minute Crustacea which swim on the surface of the water, this species, with other small forms, may be captured by using a muslin net. It is a quarter of an inch or less in length. It is easily distinguished by its large carapace, the posterior portion of which is marked off in transverse ridges, the anterior end running into a sharp-pointed rostrum. It has a long, slender abdomen, the sections of which [pg289] are distinctly marked, and it terminates in long, forked spines, which are longer than the telson. It is found from New Jersey northward.
ORDER ARTHROSTRACA
Suborder AMPHIPODA
The Amphipoda have a laterally compressed body, with gills on the thoracic feet and an elongated abdomen. The segments of the thorax are not united, nor covered by a carapace, but the whole body is covered with a segmented, polished, flexible cuticle. The three anterior legs of the abdomen are for swimming-feet, and the posterior ones are adapted for springing. The antennæ are long and hairy. The amphipods comprise the beach-fleas and many other small crustaceans which abound between tide-marks on all beaches. Besides serving in no small measure as food for fishes, they are scavengers of the beach, and consume large quantities of waste matter. They are sometimes used in preparing skeletons for anatomical specimens. Animals to be skeletonized, being fastened to boards and anchored just below the surface of the water in sheltered places, are divested of all flesh in a few hours, and the bones are more completely cleaned than if prepared by a naturalist.
Genus Orchestia
O. agilis, the beach-flea. These little crustaceans exist in countless numbers under the masses of sea-wrack on the beach. When disturbed they jump about with great agility by means of the last three pairs of abdominal feet, which are adapted to this purpose. In color the animal is brown and much resembles the decaying seaweeds among which it lives and upon which it probably feeds. The antennules are short, the antennæ long, on two long, jointed bases. The second pair of feet in the males terminate in chelæ. The last abdominal appendages are stiff and pointed backward. The abdomen is curved under. The length of Orchestia is half an inch or less. Some species occur on all beaches. O. agilis ranges from New Jersey to Greenland.
Genus Talorchestia
T. longicornis (Talitrus longicornis). This species is similar to Orchestia agilis, but is about an inch long when mature and of a paler [pg290] color. It jumps like the latter, but not so strongly. It is found among the weeds and burrowing in the sand a little below high-water mark. The wet sand is often completely filled with its holes. It can be distinguished by its very long antennæ. Another species, T. megalophthalma, is distinguished by its shorter antennæ and very large eyes. Both of these species are grayish in color and closely resemble the sand. Found from Cape Cod to New Jersey.
Genus Gammarus
G. locusta. The animals of this genus are among the largest of the amphipods. The males are larger than the females, sometimes being one and a half inches long. They are abundant under stones and Fucus at and near low-water mark. Although much larger than the beach-fleas, they otherwise resemble them. They do not jump like the former, but move rapidly, lying on the side, and in water swim with the back downward. Two pairs of the thoracic feet are chelate, and three pairs are longer than the others. The feet on the last segments of the abdomen are stiff and turn sharply back, forming a part of the tail, which is used most effectively in locomotion. The antennules and antennæ are of about the same length. Several species of Gammarus occur in the same range, all having the same general characteristics; some have but one pair of chelate feet; the antennules are usually shorter than the antennæ; the females of all the species have no chelate feet. G. locusta ranges from New Jersey to Greenland. The color is generally reddish- or olive-brown. G. annulatus is found in the same places, but usually a little higher up on the beach; it is lighter in color, and has dark bands with red spots on the sides of the abdomen. G. mucronatus occurs from Cape Cod to Florida. Melita nitida is a smaller slate-colored amphipod found in some places; another is Mœra levis, which is whitish, with black eyes.
Genus Chelura
C. terebrans, the boring amphipod. This little crustacean is associated in its work on submerged timber with the isopod Limnoria lignorum. The excavations of the latter are narrow and cylindrical, running down into the wood, while Chelura makes larger burrows in oblique lines near the surface, which give the wood the appearance of having been plowed. It is very active and destructive. It feeds upon the wood into which it burrows. Its color is semi-translucent, thickly mottled above with pink. [pg291]
Genus Caprella
C. geometrica. These very curious little animals, which are so slender as to seem like skeletons, are found in abundance clinging to hydroids, Polyzoa, delicate algæ, or eel-grass, or under stones in tide-pools. They resemble in color, and often in form, the objects on which they live. Holding on by the posterior feet, they extend the body out rigidly or sway it about, so that they resemble little sticks or branches, and often escape detection. In walking, they bring the hind feet up to the front ones, doubling the body into a loop like the canker- or measuring-worm. The appendages on the anterior and posterior ends are furnished with chelæ and hooks; those of the middle section are rudimentary. This animal cannot be mistaken for any other. C. geometrica is found from Cape Cod to North Carolina. Some of the species of this genus may be found on every coast.
Suborder ISOPODA
The isopods have an elongate, flattened, but more or less arched body, composed of seven thoracic segments and a short abdomen of six segments. The six segments of the abdomen are smaller than those of the thorax, and are often more or less united, sometimes into a single piece with scarcely any trace of division above; but the number of pairs of appendages is generally six, showing the composite nature of the apparently simple organ. The last segment, or telson, is broad and has a pair of modified appendages. The seven thoracic legs are not all equal, as the name would imply, but vary greatly in different species. As a rule, they are adapted to walking or attachment, and in the female some have delicate plates which form brood-pouches. The swimming-feet fold under the abdomen, and in some species are inclosed by the first pair, which are large and plate-like, and form a complete cover for the others. The isopods are a large and widely distributed order, varying in size, and are inconspicuous because they cling closely to objects. They are retiring in habit, though extremely ferocious.
The sow-bugs or pill-bugs, common in gardens, under leaves in the woods, and under almost any pile of rubbish among decaying vegetable matter, are a land species of isopods. Other species inhabit [pg292] ponds and streams of fresh water, and still others are found along the shores of all oceans, abounding among the marine vegetation of the shallow waters. Some swim free in the open sea; others are brought up from the greatest depths. Others, again, are parasites, and live in the internal organs of fishes and prawns. Sometimes a prawn is found having what appears like a very swollen throat, which actually is a little parasitic isopod of the family Bopyridæ attached to its gills.
Genus Cirolana
C. concharum. The body consists of fourteen segments, the first being the head, the next seven the thorax, and the last six the abdomen. On the head are the triangular eyes, the antennules, and the antennæ, and underneath is the mouth, which is covered by the maxillipeds. The dorsal surface is more or less rounded. At the bases of all the segmental thoracic rings excepting the first one are sutures marking off square, scale-like pieces (epimera). The epimera form a border to the side margins. The legs are attached to the epimera, which are, in fact, the upper segments of the legs. The first three pairs of legs have a general resemblance to one another, and are directed forward. The last four pairs are much longer and flatter, and are directed backward. The telson, or last segment, is triangular, and the square or blunt apex is fringed with hairs. On the ventral surface of the thorax in the adult females there is a long pouch for the reception and development of the eggs. This species is usually about one and a half inches in length, but sometimes is longer. Its color is yellowish, with a brown edge on the posterior margins of the segments, somewhat translucent in the thinner parts. It is found from Cape Cod to South Carolina, swimming about in shallow water, and is especially abundant in winter.