CEPHALOPODA. 175 



Fome of tlie marlstone quarries of the central counties, and the 

 lias cliffs of Dorsetshire. It is also probable that they lived in 

 a moderate depth of water, and preferred a muddy bottom to 

 rocks or coral-reefs, with which they would be apt to come in 

 perilous collision. Belemnites injured in the lifetime of the 

 animal have been frequently noticed. 



Belemnitella, D'Orb. 



Synonym, Actinocamax, Miller (founded on a mistake.) 



Type, B. mucronata, Sby. PI. II., Fig. 6. 



Distribution, Europe; North America. 6 species. Upper 

 greensand and chalk. 



The guard of the belemnitella has a straight fissure on the 

 ventral side of its alveolar border ; its surface exhibits distinct 

 vascular impressions. The phragmocone is never preserved, but 

 casts of the alveolus show that it was chambered, that it had 

 a single dorsal ridge, a ventral process passing into the fissure 

 of the guard, and an apical nucleus. 



XiPHOTEUTHIS, Hux. (1864). 



Shell with a long phragmocone enveloped in a calcareous 

 sheath. 



Fossil. 1 species. Lias. England. 



AcAiS'THOTEUTHis (Wagner), Miinster. 



Etymology, acantha, a spine, and teuthis. 



Synonyms, Kalseno (Miinster). Belemnoteuthis ? 



Type, A. prisca, Euppell. 



Eounded on the fossil hooks of a calamary, preserved in the 

 Oxford clay of Solenhofen. These show that the animal had 

 ten nearly equal arms, all furnished with a double series of 

 horny claws, throughout their length. A pen like that of the 

 ommastrephes has been hypothetically ascribed to these arms, 

 which may, however, have belonged to the lelemnite or the 

 belemnoteuthis. 



Fossil. 17 species. Oolite. 



Belemnoteuthis (Miller, Pearce, 1842). 



Type, B. antiquus (Cunnington), Fig. 40. 



Shell consisting of a phragmocone, like that of the belemnite ; 

 a horny dorsal pen with obscure lateral bands ; and a thin 

 fibrous guard, with two diverging ridges on the dorsal side. 



