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Encyclopedia Britannica - Main :: STE-SUS |
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SUBORDER I . DECAPODA.FOUr pairs of ordinary non-retractile arms which are shorter than the body
special
body
Tribe i. Oigopsida.A wide aperture in the cornea. Two oviducts in the 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 ancient forms characterized by the small size of the rostrum and proostracum, and large a (After Lankester.) ing as an invagination of the outer cell-layer. Mantle-skirt. Gill. Pen-sac or shell-sac, now closed. Dorsal groove. Primitive optic vesicle, now closed (see fig. 34). Lens. Retina. Second or anterior optic chamber still open. Iridean folds. The primitive invagination to 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. Extinct
Fam. 2. Aulacoceratidae. Extinct
Fam. 3. Belemnitidae. Extinct ; phragmacone short with ventral siphuncle, prolonged dorsally into long proostracum; rostrum large and cylindrical. Belemnites, 350 species from Jurassic and Cretaceous. Diploconus, Upper Jurassic.Fam. 4. Belopteridae. Extinct; rostrum and phragmacone well developed, phragmacone often curved; initial chamber small. Beloptera, Eocene. Bayanoteuthis, Eocene. Spirulirostra, 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 cone
long as the body ; Bathyteuthis, fins terminal, rudimentary; tentacular arms, filiform; abyssal. Rhynchoteuthis,tentacular arms united to form a beak-shaped appenda>e. Symplectoteuthis. Tracheloteuthis. Doridicus. Architeuthis; tiis is the largest of Cephalopoda
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, 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 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 organs present. Histiopsis, membrane of dorsal A, Pinnocto pus cordiformis, Quoy and Gain (from New Zealand). B, Tremocto pus violaceus, Ver. (from the Mediterranean). C, Cranchia scabra, Owen (from the Atlantic Ocean; one of the Decapoda). D, Cirrhoteuthis Mulleri, Esch. (from the Greenland coast
Fam. ii. Cranchiidae. Eight normal arms, very short; eyes prominent; fins small and terminal. Cranchia, body short, purse-shaped, normal arms short, fins entirely aboral. Loligopsis, body elongated, conical, tentacular arms slender. Leachia, tentacular arms absent, funnel without a valve. Taonius, body elongated, normal arms, rather short, eyes pedunculated. Tribe 2. Myopsida.No aperture in the cornea. Left oviduct only developed in female. Internal shell without a distinct phrag- macone, calcified or simply chitinous. Fam. t. Sepiidae. Body wide and 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. Sepia, shell with a rostrum, British. Sepiella, shell without a rostrum. Same stage as fig. 35 (4). Same stage as fig. 35 (8) ; only the left side of the sections is drawn
Rectum. Ink-sac. Outer cell-layer. Middle cell-layer. Deep cell-layer of fusiform cells (yolk-membrane). Optic nerve-ganglion. Otocyst. The " white body " of the adult ocular capsule form- A, B, al, is, ep, mes, ym, ng, ot, wb, mtf, g, Ps, dg, Poe. 1, r, 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, 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, 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 If you wish, you can link directly to this article.
<a href="http://jcsm.org/StudyCenter/Encyclopedia/STE_SUS/SUBORDER_I.html"> SUBORDER I </a> |
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