338 



THE CEPHALOPODA 



extremity of the shell are left uncovered by the mantle (Fig. 295). The 

 shell is calcareous, coiled endogastrically, multilocular and siphunculated 

 (Fig. 268, sh). The fins are posterior. Genus Spirula, Lamarck ; three 

 living species are known ; they live at great depths, and only a few entire 



individuals have been obtained : live speci- 

 mens are very rarely seen. FAMILY 6. 

 OMMATOSTREPHIDAE, Gill. The shell is in- 

 ternal and chitinous, ending aborally in a 

 little hollow cone. The tentacular arms are 

 rather short and thick. The suckers have 

 denticulate rings. Genera Ommatostrephes, 

 d'Orbigny ; fins aboral, simple, and rhom- 



Fio. 296. 



Doratopsis vermicularis (Riippel), 

 dorsal aspect. , cerebral ganglia; 

 e, eye ; Jl, fin ; nu.c, nuchal cartilage ; 

 t, tentacular arm; 1, 2, 3, 4, pair of 

 arms. (After Weiss.) 



Fio. 297. 



Ommatostrephes gagittatus, Lamarck, dorsal 

 aspect. I, mantle ; II, tentacular arm ; III, fin ; 

 IV, eye ; V, arma. (After Verauy.) 



boidal (Fig. 297) ; British. Ctenopteryx, Appellof ; fins pectinate, as long 

 as the body (Fig. 259). Hathyteuthis, Hoyle ; fins terminal, rudimentary ; 

 tentacular arms filiform ; abyssal. Rhynchoteuthis, Chun ; tentacular arms 

 united to form a beak-shaped appendage. Symplectoteuthis, Pfeiffer. Trachelo- 

 teuthis, Steenstrup. Dosidicus, Steenstrup. Architeuthis, Steenstrup ; this is 

 the giant genus among the Cephalopoda. FAMILY 7. THYSANOTEUTHIDAE, 



