1. Pharyngella monoceros, n. sp.

Shell ovate, slightly compressed, with a single large tooth on the dorsal corner of the peristome. The tooth is cylindro-conical, half as long as the shell, straight or slightly curved, and lies in the main axis of the shell. Pharynx cylindrical, straight, half as long as the shell-radius. This species is very similar to Challengeria tritonis (Pl. 99, fig. 5), and to the common cosmopolitan Challengeria naresii, but differs generically from them in the possession of the pharynx.

Dimensions.—Diameter of the shell 0.25 to 0.28; length of the tooth 0.14.

Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms.

2. Pharyngella gastrula, n. sp. (Pl. 99, fig. 18).

Shell ovate. Peristome with two parallel, vertical, straight, pointed teeth, which are half as long as the shell-radius. Pharynx of the same length, cylindrical or funnel-shaped, its outer aperture scarcely broader than the inner.

Dimensions.—Length of the shell 0.3 to 36, breadth 0.24 to 0.3; teeth and pharynx 0.07 to 0.09.

Habitat.—North Atlantic, Færöe Channel (Gulf Stream), John Murray, depth 600 fathoms.

3. Pharyngella invaginata, n. sp.

Shell circular, slightly compressed or nearly spherical. Peristome with two parallel, vertical, straight, pointed teeth, which are about as long as the shell-radius. Pharynx of the same length, funnel-shaped; its outer aperture twice as broad as the inner.

Dimensions.—Diameter of the shell 0.2 to 0.22, teeth and pharynx 0.05.

Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms.

4. Pharyngella gastræa, n. sp. (Pl. 99, fig. 17).

Shell broad, ovate or nearly circular, lenticular, strongly compressed. Peristome with two parallel, pointed teeth, which are nearly as long as the shell-radius, slightly curved, and obliquely inclined over the mouth. Pharynx half as long, cylindrical, obliquely descending; its outer and inner apertures of equal breadth.

Dimensions.—Diameter of the shell 0.3 to 0.33, teeth 0.12, pharynx 0.06.

Habitat.—South Atlantic, Stations 328 to 334, surface.

Genus 698. Porcupinia,^[315] Haeckel, 1879, Sitzungsb. med.-nat. Gesellsch. Jena, Dec. 12, p. 5.

Definition.—Challengerida with a pharynx, with teeth on the mouth and marginal spines.

The genus Porcupinia differs from the preceding Pharyngella in the development of marginal spines, and exhibits therefore the same relation to it that Challengeron bears to Challengeria. Only two species have been observed; the first of these bears, besides the large marginal spines, numerous flinty bristles on the surface of the shell.

1. Porcupinia aculeata, n. sp.

Shell ovate, one and one-third times as long as broad, slightly compressed, covered with short, bristle-shaped spines over the whole surface, similar to Entocannula hirsuta (Pl. 99, fig. 20). The keeled margin is armed with numerous long and stout radial spines, which are alternately larger and smaller, as in Challengeron moseleyi (Pl. 99, fig. 14); the larger about as long as the radius, the smaller half as long. Peristome with two straight, parallel teeth. Pharynx funnel-shaped, half as long as the radius, its outer aperture twice as broad as the inner.

Dimensions.—Length of the shell 0.24, breadth 0.18; peristome 0.05.

Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms.

2. Porcupinia cordiformis, n. sp. (Pl. 99, fig. 16).

Shell heart-shaped, nearly triangular, with a deep, concave bosom at the broad oral base, and a bunch of five to nine divergent spines at the blunt aboral apex, the middle spine (in the main axis) larger than the others. Peristome with two parallel, short, triangular teeth, which are obliquely inclined over the mouth (their upper convex edge nearly horizontal). Pharynx cylindrical, short, curved, and obliquely descending.

Dimensions.—Diameter of the shell 0.2 to 0.25, of the pharynx 0.05 to 0.08.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

Family LXXIX. Medusettida, n. fam. (Pls. 118-120).

Definition.—Phæodaria with a simple, ovate, hemispherical or cap-shaped lattice-shell of peculiar alveolate structure, and with hollow articulate feet surrounding the widely open mouth. Central capsule excentric, placed in the aboral half of the shell-cavity.

The family Medusettida represents a peculiar group of remarkable Phæodaria, which are similar to the Challengerida and Tuscarorida in the general form of the monaxonian shell and its apophyses, but differ from both families in the strange alveolate structure of the shell and of the hollow articulate feet surrounding its mouth. All the forms of this family here described are new, and not a single species was known before the discoveries of the Challenger. The majority seem to be inhabitants of the deep-sea, and occur mainly in those places where other families of Phæodaria (Aulacanthida, Aulosphærida, Cœlodendrida) are also well represented; they are, however, nowhere so common as these latter families. Their long feet and the small delicate shell are extremely fragile, so that complete and well-preserved specimens are rare. Some species are among the most admirable forms of Radiolaria, and are similar to small elegant Medusæ, e.g., Medusetta (Pl. 120, figs. 1-4), Gazelletta (Pl. 118, fig. 1), and Gorgonetta (Pl. 119).

The shell of the Medusettida is usually very small and delicate, in comparison to the long, often exceedingly large, feet, which depend from the margin of its mouth. From the size and the weight of these feet, we must suppose that the shell floats in the water in the same position as in the Nassellaria, so that the main axis is vertical, and the open mouth with the feet on its lower pole. The form of the shell exhibits the same varieties as the similar umbrella of the Medusæ. It is usually more or less hemispherical, sometimes flatter, cap-shaped, at other times more highly vaulted, campanulate or ovate. The similarity with the umbrella of a Medusa is so great, that in many species the large lower opening on the mouth of the shell is surrounded by a prominent ring or diaphragm, comparable to the velum of the Craspedotæ or Hydromedusæ (Pl. 120, figs. 3-4).

The structure of the shell, which we term shortly "alveolate," is very remarkable, and seems to be different from that of the other Phæodaria. Its reticulate appearance seems to indicate at first sight the usual lattice-shell, pierced by numerous very small pores (Pl. 118, figs. 1-3). But as soon as we make the shell dry, air always enters into its thin walls, and each apparent pore is found to be a small alveole or a separate compartment, which contains a small bubble of air (Pl. 120, figs. 11, 16). The thin wall of the shell is therefore double, composed of two parallel, very thin lamellæ of silica, which are little distant from one another, and are connected by a network of small rods or septa. This network is rarely regular, with square meshes (Pl. 118, fig. 3), or with hexagonal or triangular meshes (Pl. 116, fig. 2); it is usually irregular, with polygonal meshes (Pl. 120, figs. 11-16). The size of the meshes or alveoles is usually smallest on the aboral apex of the shell, and increases gradually towards the mouth. The largest alveoles are around the mouth, on the velum-shaped peristome, and here the marginal alveoles of the shell pass directly over into the separate alveoles or hollow compartments of the articulate feet (Pl. 118, fig. 1). Probably each alveole is a separate compartment, filled up by jelly, and has a small opening or pore on its inside; this pore is very distinct in the marginal alveoles of some larger species (Pl. 116, fig. 1a; Pl. 120, fig. 14), but I have not been able to recognise it everywhere. Moreover, it often happens that the alveoles are apparently completely closed. In some smaller species the alveolate structure seems to be present only in the peripheral part of the shell, whilst the central part is solid.

The outer convex surface of the shell is usually smooth, sometimes papillate (Pl. 116, fig. 1), at other times studded with small, conical, radial spines (Pl. 118, fig. 1; Pl. 120, figs. 4-11). Prolonged cylindrical spines or tubes are rarely scattered over the surface (Pl. 116, figs. 1, 2). In some genera a long vertical or oblique spine is developed from the apex of the shell, and is comparable to the "apical horn" of the Nassellaria (Pl. 118, figs. 2, 3; Pl. 120, figs. 1-4).

The mouth of the shell, or the large opening on the lower pole of its vertical main axis, is usually widely open, circular or polygonal, more rarely constricted. In many species the peristome is broadened and its margin developed in the form of a horizontal diaphragm, which constricts the entrance into the shell-cavity, and is comparable to the velum of the Hydromedusæ (Pl. 120, figs. 1-4). Sometimes the margin of the velum is fringed and bears numerous small dependent filaments of silica, comparable to the marginal tentacles of many Medusæ (Pl. 118, figs. 1, 3; Pl. 120, fig. 16). Rarely the mouth is strongly constricted and prolonged into a narrow, long, cylindrical tube, comparable to a proboscis; its opening is usually fringed (Pl. 116, figs. 1, 2).

The hollow articulate feet, or the large radial apophyses of the peristome, are the most remarkable organs of the Medusettida, and occur in the same form in no other family of Radiolaria. Their number is variable from three to twelve or more, and is here employed for the distinction of genera, as it is rather constant; the most frequent number is four (Medusetta) or six (Gazelletta). The feet are usually cylindrical, much longer than the shell, and more or less curved; more rarely they are straight or slightly compressed. They are always articulate, and divided by numerous transverse parallel septa into hollow compartments or alveoles; the transversely striated appearance of the feet is brought about by these septa. The alveoles have usually the form of short discoidal cylinders, and are broader than long (Pl. 120, figs. 5-13); rarely they are longer than broad (fig. 15). The septa between the alveoles are always perforated by a small opening and usually this opening is prolonged into a shorter or longer tubule, comparable to the siphuncle in the septa of the chambered shells of Cephalopoda; as in these latter, the succeeding siphons are arranged in a continuous series, which lies either in the axis of the foot or parallel to it (Pl. 120, figs. 8, 13, 15). The siphons are directed towards the distal end of the foot, so that, e.g., the siphon which arises from the septum between the ninth and tenth alveole, projects into the cavity of the latter. The communicating cavities of all the alveoles are filled up by jelly. In the dry shells, which are cleaned by hot mineral acids or by fire, and in which, therefore, the jelly is destroyed, the cavities become easily filled by air-bubbles (Pl. 120, figs. 8, 11, 15). Whilst the alveoles of each foot always form a long simple series, this series becomes doubled on the base of the larger feet, where they are broadened, and pass over into the compartments of the peristome (Pl. 122, figs. 10, 11, 14). The terminal alveole of each foot is closed.

The feet of the Medusettida are rarely quite simple and smooth (Pl. 120, figs. 1, 5, 7, 10, &c.). Usually they are armed with numerous spines or with elegant pencils of spathillæ. These secondary appendages or branches are also hollow, with a thin wall of silex; but they seem usually not to communicate with the alveoles of the foot directly; the cavities of the foot and its appendages are separated by a thin, solid septum. In Medusetta the convex outer edge of each curved foot is studded with a series of simple alveolate branches (Pl. 120, figs. 2-4). In Gazelletta, the feet are usually armed with verticillate or alternate spines, which are either simple or branched (Pl. 120, figs. 11-15); sometimes each branch is elegantly arborescent (Pl. 118, fig. 1). Sometimes the distal end of each branch is armed with a spathilla or a coronet of recurved teeth. The branches attain their highest development in the admirable Gorgonetta (Pl. 119). The twelve feet of this most interesting genus are differentiated into two different and alternating groups, six descending and six ascending. The six upper or ascending feet are arborescent, and each branch is armed at the distal end with a spathilla (figs. 1, 2). The six lower or descending feet are covered with most elegant arborescent pencils or anchor-bearing trees; each terminal branch of a tree is armed with two spathillæ, a smaller terminal and a larger below it (figs. 3, 4). The distal ends of the feet are rarely simple, usually they are forked or branched, or armed with peculiar spathillæ; and sometimes these terminal branches are very large (Pls. 118, 119).

The central capsule of the Medusettida is usually subspherical or somewhat lenticular, and hidden in the aboral or upper part of the shell-cavity, whilst its oral or lower part is filled up by the phæodium (Pl. 120, figs. 2, 9, 10, 11). Sometimes the phæodium is very large and prominent at the aperture of the mouth (Pl. 118, figs. 2, 3; Pl. 119, fig. 1). The nucleus is usually ellipsoidal, half as large as the central capsule, and includes numerous nucleoli. The membrane of the central capsule seems in all Medusettida to possess only one opening, the astropyle or main-opening with a radiate operculum and proboscis, placed at the lower or oral pole (Pl. 120, fig. 2). I have never been able to observe any secondary opening or parapyle. The free space between the shell wall and the capsule is filled up by the calymma, which also includes the phæodium. The jelly of the calymma is probably in direct continuity with the jelly which fills up the alveoles of the shell-wall and of the articulate feet.

Synopsis of the Genera of Medusettida.

Genus 699. Cortinetta,^[316] n. gen.

Definition.—Medusettida with three articulate feet on the peristome.

The genus Cortinetta comprises Medusettida which exhibit the minimum number of feet, three, and which therefore may be compared to the tripodal Nassellaria (Cortina, Cortiniscus, Tripodiscus, &c.). This similarity is the greater, as in the few observed species an apical horn is developed (as also in the following genus). The three feet are in the two species observed of equal size and similar form, and equidistant, so that they cannot be distinguished as an odd caudal and two paired lateral feet, as in the similar Nassellaria.

1. Cortinetta tripodiscus, n. sp. (Pl. 117, fig. 7).

Shell campanulate, covered with numerous curved ascending bristles, with a prominent annular velum on the peristome, similar to that of Medusetta craspedota. (Pl. 120, fig. 4). Feet equal, widely divergent and equidistant, somewhat longer than the shell, slightly curved, and covered on their convex outer edge with a series of short lateral branches, the three ramules of which bear a spathilla. Apical horn conical, straight, about as long as the shell, also covered with curved bristles.

Dimensions.—Length of the shell 0.14, breadth 0.11; length of the feet 0.16, of the apical horn 0.11.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

2. Cortinetta cortiniscus, n. sp.

Shell campanulate, subspherical, thorny, with a prominent annular velum on the peristome. Feet equal, very large, widely divergent, about three times as long as the shell and studded with arborescent branches, similar to those of Gazelletta drymonema (Pl. 118, fig. 1). Apical horn slender, conical, straight, thorny, twice as long as the shell.

Dimensions.—Length of the shell 0.18, breadth 0.16; length of the feet 0.5 to 0.6, of the apical horn 0.33.

Habitat.—Central Pacific, Station 274, depth 2750 fathoms.

Genus 700. Medusetta,^[317] n. gen.

Definition.—Medusettida with four equidistant articulate feet of equal size on the peristome.

The genus Medusetta comprises those forms of the family which bear on the peristome four equal radial feet, and therefore exhibit a striking similarity to many small Medusæ (e.g., Codonium, Tiara, Sarsia, &c.). This similarity is the greater, as usually the four feet are elegantly curved and the entrance in the shell-cavity partly closed by a marginal diaphragm, comparable to the velum of the Craspedotæ or Hydromedusæ. In all the species observed the apex of the shell bears a slender vertical or curved spine, comparable to the apical horn of the Nassellaria. In most species the feet bear on their convex outside a series of teeth or branches, which are also alveolate.

1. Medusetta codonium, n. sp. (Pl. 120, fig. 1).

Shell ovate, smooth, twice as broad as the constricted mouth. Apical horn about as long as the shell, nearly straight, smooth. Feet cylindrical, smooth, irregularly curved, about as long as the shell.

Dimensions.—Length of the shell 0.08, breadth 0.05.

Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms.

2. Medusetta tiara, n. sp.

Shell campanulate, smooth, about as long as broad, and three times as broad as the constricted mouth, which is surrounded by a horizontal broad ring, like the velum of a Hydromedusa. Apical horn conical, straight, half as long as the shell. Feet divergent, irregularly curved, twice as long as the shell.

Dimensions.—Length of the shell 0.07, breadth 0.06.

Habitat.—North Atlantic (Færöe Channel), John Murray, surface.

3. Medusetta minima, n. sp.

Shell slenderly ovate, smooth, about twice as long as broad, twice as broad as the constricted mouth. Apical horn straight, vertical, of the same length. Feet somewhat longer, very thin, slightly curved at the base, in the distal half nearly parallel and descending vertically.

Dimensions.—Length of the shell 0.06, breadth 0.03.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

4. Medusetta quadrigata, n. sp. (Pl. 120, fig. 2).

Shell ovate, campanulate, smooth, little broader than the wide open mouth. Apical horn longer than the shell, more or less curved, smooth. Feet cylindrical, about as long as the shell, strongly curved and somewhat spirally revoluted, with a series of short curved teeth on the abaxial margin.

Dimensions.—Length of the shell 0.07 to 0.09, breadth 0.04 to 0.06.

Habitat.—North Pacific (off Japan), Stations 231 to 237, surface.

5. Medusetta tetranema, n. sp. (Pl. 120, fig. 3).

Shell campanulate, conical, smooth, nearly twice as broad as the constricted mouth, without prominent velum. Apical horn somewhat shorter, straight, conical, thorny. Feet strongly curved inwards, convergent, twice as long as the shell, each with four to six strong, ascending, alveolate branches on the abaxial margin.

Dimensions.—Length of the shell 0.07 to 0.09, breadth 0.05 to 0.07.

Habitat.—Tropical Atlantic, Station 352, surface.

6. Medusetta spiralis, n. sp.

Shell hemispherical, thorny, with wide open mouth. Apical horn straight, vertical, thorny, twice as long as the shell; feet cylindrical, three times as long as the shell, spirally convoluted around the vertical axis of the shell, with a series of recurved teeth on the abaxial margin.

Dimensions.—Length of the shell 0.05, breadth 0.08.

Habitat.—Central Pacific, Stations 271 to 272, surface.

7. Medusetta craspedota, n. sp. (Pl. 120, fig. 4).

Shell campanulate or nearly spherical, spiny, twice as broad as the constricted mouth, which is surrounded by a funnel-shaped truncate velum. Apical horn conical, straight, spiny, half as long as the shell. Feet strongly curved, longer than the shell, with a series of short conical spines on the abaxial side.

Dimensions.—Length of the shell 0.06, breadth 0.06.

Habitat.—North Pacific, Station 239, surface.

Genus 701. Euphysetta,^[318] n. gen.

Definition.—Medusettida with four articulate feet on the peristome, one odd very large, and three small or rudimentary feet.

The genus Euphysetta agrees with the preceding Medusetta in the possession of four articulate feet; but whilst these in the latter are of equal size and similar shape, in the former a single odd foot only is developed, and very large, whilst the three others are rudimentary and very small. Euphysetta exhibits therefore the same relation to Medusetta that the Euphysidæ (Euphysa, Steenstrupia, &c.) bear to the Sarsiadæ (Codonium, Sarsia), among the Hydromedusæ (compare my System der Medusen, 1879, vol. i. p. 12).

1. Euphysetta staurocodon, n. sp. (Pl. 118, fig. 2).

Shell ovate, nearly as broad as long, smooth, with an oblique, slender, conical, apical horn of the same length. The larger odd foot cylindrical, curved, somewhat longer than the shell, with three diverging branches at the distal end. The three smaller feet very short, representing the form of a regular rectangular cross.

Dimensions.—Length of the shell 0.15, breadth 0.14.

Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms.

2. Euphysetta hybocodon, n. sp.

Shell ovate, one and one-third times as long as broad, smooth, with an oblique, stout, conical horn of half the length. The larger odd foot cylindrical, curved, twice as long as the shell, with a few pairs of short lateral branches and forked distal end. The three smaller feet half as long as the shell, thorny.

Dimensions.—Length of the shell 0.16, breadth 0.12.

Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms.

3. Euphysetta amphicodon, n. sp. (Pl. 118, fig. 3).

Shell subspherical, smooth, with a short, oblique, conical, apical horn. The larger odd foot cylindrical, nearly straight, as long as the shell, with a few short lateral branches, at the distal end forked. The three smaller feet were in one specimen observed forked, in another (the specimen figured) replaced by nine small thorns.

Dimensions.—Length of the shell 0.11, breadth 0.13.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

Genus 702. Gazelletta,^[319] John Murray, 1876 (in litteris).

Definition.—Medusettida with six articulate feet on the peristome.

The genus Gazelletta is by far the most common of all Medusettida, and some species seem to be widely distributed, or even cosmopolitan. The number of species, too, is in this genus much larger than in all the other genera of this family. It differs from the latter in the possession of six feet, which number is very constant in the majority of species; in some species, however, single specimens are not rarely found which possess five or seven feet instead of six. Usually the six feet are rather regularly formed and disposed, and diverge downwards; but sometimes there is more or less irregularity in their shape and arrangement. In the majority of species the feet are very long, curved, and armed in a very various manner, so that four subgenera may be distinguished, according to the armatures.

Subgenus 1. Gazellarium, Haeckel.

Definition.—Feet simple, smooth, without spines and without terminal branches.

1. Gazelletta hexanema, n. sp. (Pl. 120, fig. 5).

Shell hemispherical, smooth. Feet very long, cylindrical, straight, smooth, widely divergent, without terminal branches.

Dimensions.—Length of the shell 0.03 to 0.04, breadth 0.06 to 0.07; length of the feet 0.1 to 0.2.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, surface.

2. Gazelletta macronema, n. sp. (Pl. 120, figs. 7, 8).

Shell hemispherical, smooth. Feet very long, cylindrical, smooth, in the basal part horizontally expanded, in the distal part strongly curved downwards, without terminal branches.

Dimensions.—Diameter of the shell 0.1 to 0.12, length of the feet 1.2 to 1.6.

Habitat.—Central Pacific, Stations 270 to 274, surface.

3. Gazelletta orthonema, n. sp. (Pl. 120, fig. 10).

Shell hat-shaped, thorny. Feet cylindrical, straight, smooth, widely divergent, without terminal branches.

Dimensions.—Diameter of the shell 0.12 to 0.16, length of the feet 0.3 to 0.5.

Habitat.—Central Pacific, Stations 270 to 274, surface.

4. Gazelletta cyrtonema, n. sp. (Pl. 120, fig. 9).

Shell hat-shaped, thorny. Feet cylindrical, smooth, widely diverging at the base, strongly curved and convergent in the distal part, often semicircular, without terminal branches.

Dimensions.—Diameter of the shell 0.11 to 0.13, length of the feet 0.4 to 0.6.

Habitat.—North Atlantic, Station 354, Canary Islands, surface.

Subgenus 2. Gazellidium, Haeckel.

Definition.—Feet smooth, without lateral spines, but branched at the distal end, or with a bunch of terminal spines.

5. Gazelletta furcata, n. sp.

Shell flat, cap-shaped, smooth. Feet cylindrical, nearly straight, at the distal end forked, with two divergent, spinulate, terminal branches.

Dimensions.—Length of the shell 0.12, breadth 0.3; length of the feet 0.6 to 0.8.

Habitat.—Western Tropical Pacific, Station 224, surface.

6. Gazelletta bifurca, n. sp. (Pl. 120, fig. 6).

Shell cap-shaped, thorny. Feet nearly straight, widely divergent, cylindrical, smooth, at the distal end twice forked, with four divergent, terminal branches, each of which bears a spathillum with six to eight recurved teeth (sometimes, as in the specimen figured, five or six terminal branches instead of four).

Dimensions.—Diameter of the shell 0.1, length of the feet 0.3 to 0.4.

Habitat.—South Pacific, Station 288, surface.

7. Gazelletta penicillata, n. sp.

Shell campanulate, spiny. Feet cylindrical, strongly curved, smooth, with a bunch of twelve to twenty or more curved spines at the distal end.

Dimensions.—Diameter of the shell 0.08, length of the feet 0.6.

Habitat.—Central Pacific, Station 266, surface.

Subgenus 3. Gazellonium, Haeckel.

Definition.—Feet spiny, armed with simple or branched lateral spines, and with terminal branches of the same shape.

8. Gazelletta pectinata, n. sp.

Shell flat, cap-shaped, thorny, three times as broad as high. Feet straight or slightly curved, cylindrical, widely divergent, with four longitudinal rows of short and simple conical spines, which are directed towards the distal end, and about as long as a single joint of the foot.

Dimensions.—Length of the shell 0.16, breadth 0.5; length of the feet 1.5 to 2.0, breadth 0.03 to 0.05.

Habitat.—North Atlantic, Færöe Channel (John Murray), Hebrides (Mœbius).

9. Gazelletta pinnata, n. sp.

Shell hat-shaped, thorny. Feet cylindrical, strongly curved, pinnate, with two opposite longitudinal rows of simple conical spines, which are slightly curved, directed towards the distal end and opposed in pairs on about each third or fourth joint.

Dimensions.—Diameter of the shell 0.3, length of the feet 1.2 to 1.5.

Habitat.—South Atlantic, Station 325, depth 2650 fathoms.

10. Gazelletta studeri, n. sp. (Pl. 120, fig. 15).

Shell flat, cap-shaped, thorny. Feet widely divergent, nearly straight and horizontally expanded, with two alternate longitudinal rows of lateral spines, which arise perpendicularly from the foot, are simple, conical, slightly curved, and alternate on the succeeding joints. Ends of the feet constricted, with four to six spines in one row. Dedicated to Professor Studer.

Dimensions.—Diameter of the shell 0.15, length of the feet 0.6 to 0.8.

Habitat.—South Atlantic (east of Patagonia), Station 318, surface.

11. Gazelletta schleinitzii, n. sp. (Pl. 120, figs. 11, 12).

Shell hat-shaped, thorny. Feet cylindrical, nearly straight and horizontally expanded, with four longitudinal rows of equal lateral spines, which arise perpendicularly from the foot and bear at the end three short divergent teeth. The end of the arms bears three forked spines. I name this elegant species in honour of Captain Schleinitz, commander of the German ship "Gazelle," who conducted the deep-sea soundings during the years 1874 to 1876.

Dimensions.—Diameter of the shell 0.12, length of the feet 0.6 to 0.8.

Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms.

12. Gazelletta trispathilla, n. sp. (Pl. 120, fig. 13).

Shell flat, cap-shaped, smooth. Feet cylindrical, nearly straight, widely divergent, with longitudinal rows of alternate spines, which arise perpendicularly from the foot and bear at the end three short divergent branches, each with a spathilla of six short teeth.

Dimensions.—Diameter of the shell 0.2 to 0.25, length of the feet 1.2 to 1.5.

Habitat.—North Pacific, Station 235 to 238, surface.

13. Gazelletta robusta, n. sp. (Pl. 120, fig. 14).

Shell flat, cap-shaped, thorny. Feet cylindrical, very stout, slightly curved, covered with short irregularly branched spines; their ends with a bunch of similar spines.

Dimensions.—Diameter of the shell 0.6, length of the feet 2.5 to 3.3.

Habitat.—Central Pacific, Stations 263 to 274, surface.

Subgenus 4. Gazellusium, Haeckel.

Definition.—Feet spiny, armed with simple or branched lateral spines, and with larger terminal branches of a different shape.