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SUBORDER I

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Originally appearing in Volume V05, Page 702 of the 1911 Encyclopedia Britannica.
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SUBORDER I . DECAPODA.—FOUr pairs of See also:

ordinary non-retractile arms which are shorter than the See also:body, and one pair of tentacular arms, situated between the third and See also:fourth normal arms on each See also:side and retractile within See also:special pouches. Suckers pedunculated and provided with horny rings, on the tentacular arms confined usually to the distal extremities. Usually a well-See also:developed See also:internal See also:shell, and lateral fins on the edges of the body. See also:Heart in a coelomic cavity; nidamentary glands usually See also:present. Tribe i. Oigopsida.—A wide See also:aperture in the cornea. Two oviducts in the See also:female. In fossil genera and Spirula, shell has a multi-!ocular phragmacone with a siphuncle; initial chamber globular and larger than the second chamber. The most See also:ancient forms characterized by the small See also:size of the rostrum and proostracum, and large a (After Lankester.) See also:ing as an invagination of the See also:outer See also:cell-layer. See also:Mantle-skirt. Gill.

See also:

Pen-See also:sac or shell-sac, now closed. Dorsal groove. See also:Primitive optic vesicle, now closed (see fig. 34). See also:Lens. Retina. Second or anterior optic chamber still open. Iridean folds. The primitive invagination to See also:form one of the otocysts, as seen in fig. 35 (5) and (6). size of the phragmacone. In the living genera, except Spirula, the shell is a chitinous gladius.

Fam. I. Belemnoteuthidae. See also:

Extinct; shell with well-developed phragmacone, and rostrum merely a calcareous envelope; siphuncular necks directed backwards as in Nautiloidea; ten equal arms provided with hooks. Phragmoteuthis, Trias. Belemnoteuthis, See also:Jurassic and Cretaceous. Acanthoteuthis, Jurassic. Fam. 2. Aulacoceratidae. Extinct; phragmacone with widely separated septa; rostrum well developed and claviform. Aulacoceras, Trias.

Atractites, Trias and Jurassic. Xiphoteuthis, See also:

Lias. Fam. 3. Belemnitidae. Extinct ; phragmacone See also:short with ventral siphuncle, prolonged dorsally into See also:long proostracum; rostrum large and cylindrical. Belemnites, 350 See also:species from Jurassic and Cretaceous. Diploconus, Upper Jurassic. Fam. 4. Belopteridae. Extinct; rostrum and phragmacone well developed, phragmacone often curved; initial chamber small.

Beloptera, See also:

Eocene. Bayanoteuthis, Eocene. Spirulirostra, See also:Miocene. Fam. 5. Spirulidae. Dorsal and ventral sides of posterior extremity of shell uncovered by mantle; no rostrum or proostracum; shell calcareous, coiled endogastrically and siphunculated; fins posterior. Spirula, three living species known, abyssal. Fam. 6. Ommatostrephidae. Shell internal and chitinous, ending aborally in a little narrow See also:cone; tentacular arms short and thick; suckers with denticulate rings.

Ommatostrephes, fins aboral, See also:

simple and rhomboidal, See also:British. Ctenopteryx, fins pectinate, as long as the body ; Bathyteuthis, fins terminal, rudimentary; tentacular arms, filiform; abyssal. Rhynchoteuthis,tentacular arms See also:united to form a See also:beak-shaped appenda>e. Symplectoteuthis. Tracheloteuthis. Doridicus. Architeuthis; tiis is the largest of See also:Cephalopoda, reaching 6o ft. in length including arms. Fam. 7. Thysanoteuthidae. Arms enlarged, bearing two rows of suckers and filaments; fins triangular, extending whOle length of body. Thysanoteuthis, Mediterranean.

Fam. 8. Onychoteuthidae. Fins terminal; tentacular arms long; suckers with hooks. Onychoteuthis, See also:

hook-bearing suckers on tentacular arms only. Enoploteuthis, hook-bearing suckers on all the arms. Veranya, body very short, tentacular arms atrophied in the adult, Mediterranean. Chaunoteuthis, body elongated, tentacular arms atrophied. Pterygioteuthis. Ancistroteuthis. Abralia. Teleoteuthis.

Lepidoteuthis. Fam. 9. Gonatidae. Body elongated; . fins terminal; radula with only two lateral See also:

teeth. Gonatus. Fam. to. Cheiroteuthidae. Tentacular arms long, not retractile; resisting apparatus well developed. Cheiroteuthis, suckers along the whole length of the tentacular arms. Doratopsis, body very long and slender with aboral spine, dorsal arms very short. Histioteuthis, six dorsal arms united by membrane, photogenous See also:organs present.

Histiopsis, membrane of dorsal A, Pinnocto pus cordiformis, Quoy and Gain (from New See also:

Zealand). B, Tremocto pus violaceus, Ver. (from the Mediterranean). C, Cranchia scabra, See also:Owen (from the See also:Atlantic Ocean; one of the Decapoda). D, Cirrhoteuthis Mulleri, Esch. (from the See also:Greenland See also:coast). arms only See also:half-way up the arms, photogenous organs present. Calliteuthis, no brachial membrane, photogenous organs present. Grimalditeuthis, two fins on each side, no tentacular arms. Fam. ii. Cranchiidae. Eight normal arms, very short; eyes prominent; fins small and terminal. Cranchia, body short, See also:purse-shaped, normal arms short, fins entirely aboral.

Loligopsis, body elongated, conical, tentacular arms slender. Leachia, tentacular arms absent, See also:

funnel without a See also:valve. Taonius, body elongated, normal arms, rather short, eyes pedunculated. Tribe 2. Myopsida.—No aperture in the cornea. See also:Left oviduct only developed in female. Internal shell without a distinct phrag- macone, calcified or simply chitinous. Fam. t. Sepiidae. Body wide and See also:flat; fins narrow, extending the whole length of the body; shell calcareous and laminated. Belosepia, a rudiment of rostrum and phragmacone present in shell, Eocene. See also:Sepia, shell with a rostrum, British.

Sepiella, shell without a rostrum. Same See also:

stage as fig. 35 (4). Same stage as fig. 35 (8) ; only the left side of the sections is See also:drawn, and the See also:food-material which occupies the space internal to the membrane ym is omitted. Rectum. See also:Ink-sac. Outer cell-layer. See also:Middle cell-layer. Deep cell-layer of fusiform cells (yolk-membrane). Optic See also:nerve-ganglion. Otocyst.

The " See also:

white body " of the adult ocular See also:capsule form- A, B, al, is, ep, See also:mes, ym, ng, ot, wb, mtf, g, Ps, dg, See also:Poe. 1, r, See also:soc, 702 Fam. 2. Sepiolidae. Body short, rounded at the aboral end; fins rounded, inserted in middle of body-length; shell chitinous, small or absent. Sepiola, See also:head united to mantle dorsally, British. Rossia, head not united to mantle, British. Stoloteuthis and Inioteuthis, without shell. Heteroteuthis. Euprymna. Fam. 3.

Idiosepiidae. Body elongated, with rudimentary terminal fins; internal shell almost lost. Idiosepius, 1.5 cm. long, See also:

Indian Ocean. Fam. 4. Sepiadariidae. Body short; mantle united to head dorsally; no shell. Sepiadarium, Pacific Ocean. Sepioloidea, Australian. Fam. 5. Loliginidae.

Body elongated and conical; fins extending forward beyond the middle of body-length; shell chitinous, well developed. Loligo, fins triangular, aboral, British. Sepioteuthis, fins rounded, extending along whole of body-length. Loliolus. Loliguncula. The following fossil genera, known only by their gladius and ink-sac, have been placed near Loligo :—Teuthopsis, Beloteuthis and Geoteuthis, Lias; Phylloleuthis, Cretaceous; Plesioteuthis, Jurassic and Cretaceous.

End of Article: SUBORDER I

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