202 HELICERAS, BELEMNITELLA. FTC. 



Section I. ACCELI, Bronn. Rostrum without dorsal or ventral grooves 

 at its anterior end. 



Subsection 1. Acuarii, Orb. Rostrum more or less conical, with- 

 out lateral furrows, but often channeled at the posterior end. 

 Jura., Chalk, 20 species. 



Subsection 2. Clavati, Orb. Shell lengthened, with lateral fur- 

 rows. Lias., 3 species. 



Section II. GASTROCCELI, Orb. Rostrum with an anterior ventral 

 groove. 



Subsection 3. Canaliculati, Orb. Rostrum without lateral grooves. 

 Jura., 5 species. 



Subsection 4. Hastati, Orb. With two long lateral grooves. 



Jura., Chalk, 19 species. 

 Section III. NOTOCCELI, Orb. With a deep dorsal groove. 



Subsection 5. Dilatati, Orb. With lateral grooves. Neocomian, 

 9 species. 



B. EXCENTRTCUS. PL 95, tig. 4;")."). Oxford. Oolite of England. 

 B. SEMIHASTATUS. PL 95. figs. 4f)('.. 457. J m-assic of Wut'tembvrf/. 

 B. SEMIHASTATUS. PhraguH K-OUC ; view of si phonal side (iig. 457). 



Genus HELICERAS, Dana. 



H. FUGIKNSJS, Dana. PL 95, fig. 458. Ii shite rock. Gape 

 Horn. Only species. 



Genus BELEMNITELLA, d'Orb. 



Six species are found in the upper oreeiisaiid and chalk of 

 Europe and North America. 



B. MUCRONATA, Sowb. PL 95. fig. 459. Mm'xtrwhL 



Geftus XIPHOTEUTHIS. Huxley. 

 Founded on a single English liassic species. 

 X. ELONGATA, De la Beclie. PL 95, fig. 4C.O. I^jnm Regis. 



Genutf ACANTHOTEUTHIS, AVa^iH-i'. 

 Oolitic. Seventeen species. 



A. ANTIQUUS, Cunniiigton. PL 95, Iig. 461. Oxford clay of 

 Wiltshire, Eng. 



