108 CLASSIFICATION. 



Family XII. BELOSEPIID.E. 



BELOSEPIA. (Fossil only.) General characters those of the family. Doubt- 

 fully separable from Sepia. 



COCCOTEUTHIS. (Fossil only.) Shell like Belosepia, thickened ventrally 

 by horny, instead of chalky layers. 



Family XIII. BBLEMNITID -K. 



BELEMNITES. (Fossil only.) Animal, arms and tentacles with two rows 

 of horny hooks. Shell, phragmocone horny and slightly nacreous, with 

 a minute globular initial chamber ; two nacreous bands on its dorsal 

 side, and produced beyond its rim into swonl-shaped processes, repre- 

 sent the rostrum, which is fibrous, cylindrical, thickened behind, thin 

 in front where it invests the phragmocone . 



BELEMNITELLA. (Fossil only.) Rostrum with a straight fissure on the 

 ventral side of its alveolar border ; its surface with distinct vascular 

 impressions. Casts of the alveolus show that the phragmocone was 

 chambered, had a single dorsal ridge, and a ventral process entering 

 the fissure of the rostrum. 



XIPHOTEUTHIS. (Fossil only.) Rostrum or pro-ostracum calcareous, 

 phragmocone very long and narrow. 



ACANTHOTEUTHIS. (Fossil only.) Animal with ten nearly equal arms 

 with two rows of horny hooks and suckers ; margin of mantle free all 

 around ; fins large, medio-dorsal. Shell a phragmocone like Belemmtes, 

 a horny dorsal pen with obscure lateral bunds and a thin iibrous 

 rostrum with two diverging dorsal ridges. 



CONOTETJTHIS. (Fossil only.) Phragmocone slightly curved, chambered 

 and siphunculated, with an elongated, slender pen. No protecting 

 rostrum. 



BELEMNOSIS. (Fossil only.) Phragmocone straight or slightly curved ; 

 rostrum rather long, thickened dorsally and obtuse at the hinder end, 

 with a ventral opening. 



BELOPTERA. (Fossil only.) Shell straight, rostrum sometimes winged 

 on the sides, bluntly beaked at the hinder end. 



SPIRULIROSTRA. (Fossil only.) Phragmocone commencing with a spiral 

 like Spirula, afterwards continuing straight ; external spathose layer 

 produced posteriorly into along, pointed end. 



HELICERUS. (Fossil only.) Shell like Belemmtes, half inch in diameter : 

 guard thick, subcylindrical, fibrous ; phragmocoue slender, terminating 

 in a fusiform spiral nucleus. 



Family XIV. SPIRULIIU:. 

 SPIRULA. (Recent.) Characters those of the family. 



