Tribe 2. Myopsida.—No aperture in the cornea. Left oviduct only developed in female. Internal shell without a distinct phragmacone, calcified or simply chitinous.
Fam. 1. 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.
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; Phylloteuthis, Cretaceous; Plesioteuthis, Jurassic and Cretaceous.
Suborder 2. Octopoda.—Only four pairs of arms, all similar and longer than the body. Body short and rounded aborally. Suckers sessile. Heart not contained in coelom. No nidamentary glands.
| Fig. 39.—Palaeoctopus Newboldi, the oldest Octopod known. From the Cretaceous rocks of Lebanon. (After H. Woodward.) |
Tribe I. Leioglossa.—No radula. Arms united by a complete membrane. Fins on sides of body.