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. Famity 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, 
dOrbigny ; fins aboral, simple, and rhom- 
Fic. 296. 
Doratopsis vermicularis (Riippel), Fic. 297. 
dorsal aspect. ce, cerebral ganglia ; : 
e, eye; fi, fin; nz.c, nuchal cartilage ; Ommatostrephes sagittatus, Lamarck, dorsal 
t, tentacular arm; 1, 2, 3, 4, pair of aspect. I, mantle; Il, tentacular arm; III, fin; 
arms. (After Weiss.) IV,eye ; V, arms. (After Verany.) 
boidal (Fig. 297); British. Otenopteryx, Appellof ; fins pectinate, as long 
as the body (Fig. 259). Bathyteuthis, Hoyle ; fins terminal, rudimentary ; 
tentacular arms filiform ; abyssal. Rhynchoteuthis, Chun ; tentacular arms 
united to form a beak-shaped appendage. Symplectoteuthis, Pfeiffer. T'rachelo- 
teuthis, Steenstrup. Dosidicus, Steenstrup. Architeuthis, Steenstrup ; this is 
the giant genus among the Cephalopoda. Famity 7. THYSANOTEUTHIDAE, 
