MARINE MOLLUSCA OP THE UNITED STATES. 9 



Mantle famished with three internal cartilages, one dorsal and 

 two ventral. Siphuncle with a valve. Fins angular. 



Family Loliginid^e. Eyes covered with skin, simple. Mantle 

 with three internal cartilages, one dorsal and two ventral. 



* Shell internal, calcareous, spiral, chambered, siphunculated. 



Famil}^ Spirulid^. Eyes covered with the skin, with a lower 

 eyelid. Mantle free all around. 



Family LOLIGOPSID.E. 



The members of this family have the eyes pedunculated and 

 not covered by a skin; the fins are caudal, terminal, and semi- 

 circular ; the body is membranaceous, semipellucid, elongate, and 

 tapering behind. They inhabit the high seas, and are powerful 

 swimmers. 



Genus LOLIGOPSIS, Lamarck. 

 Extr. de Cours. 1813. 



LeacMa, Lesueur, Journ. Philad. Acad., ii. 89. 1831. 



Bod}^ very long, conical, attenuated. Shell flexible, slender, 

 keeled above; very narrow, lanceolate, thickened at the tip. 



1. L. PAYO, Lesueur. Fig. 3. 



(Loligo.) Journ. Philad. Acad., ii. 96. 1831. 



Body smooth, spotted with red. Fins terminal, short, soft, 

 narrow, outline together heart-shaped, not notched in front. Ses- 

 sile arras slender, short, three upper pairs rounded. Cups much 

 depressed, broad, oblique ; rings smooth exterioijly, inner edge 

 divided into square teeth. Tentacular arms slender. Shell elon- 

 gate, very thin, nearly gelatinous, attenuated anteriorly, lanceo- 

 late posteriorly. 



Arctic Seas, New England, Neio York, Madeira. 



Family ONYCHOTEUTHID.E. 



Synopsis of Genera. 

 * Tentacxilar Arms icith Hooks. Sessile Arms icith Cups and Rings. 

 Club of tentacular arm with hooks. Shell lanceolate, pennate, sides thin. 



Onychoteuthis. 

 Club of tentacular arm with hooks on the centre, and with two rows of 

 small cups on each side. ' Shell lanceolate, pennate. Onychia. 



* Tentacular and sessile arms with cups and horny rings. 



