OYRTOCERAS. ONOOCERAS, ETC. 211 



PILOCEEAS, Salter. 



Shell broad. conical. subcylindrical or compressed, slightly 

 curved. The siphuncle and septa represented by a scries of 

 conical septa, concave to a central point. 



Fossil, three species. L. Silurian. Canada; Scotland. 

 PILOCERAS. Ideal section. PL 97, tig. 486. 



Genus CYRTOCERAS, Goldi'uss. 



Shell curved ; siphuucle small. subcentral. 



Fossil, eighty-four species. L. Silurian to ( 1 arl>. N. and S. 

 America ; Europe. 



Seems to differ but little from Orthoceras. 

 < . AcuTicosTATLM. Sandb. PI. 97. fig. 487. 



Subgenera : 

 Oncoceras, Hall. 



Anterior hnlf of the shell inflated, aperture more or less 

 strangulated. This m;i\ possibly = Phragmoceras. Brod. 



Silurian. New York. Three species. 

 O. roNSTUH'Ti .M. Hall. PI. 97. fig. 4SS. 



Cyrtocerina, Billings. 



Shell short and thick, with a larii'e siphiincle, placed dorsally. 

 Two species. Silurian. Canada. 



Streptoceras, Billings. 



Shell like Oncoceras. but the aperture trilohed. 

 Two species. Middle Silurian. Canada. 



Genus GOMPHOCERAS, J. Sowb. 



Shell fusiform or bottle-shaped, straight, swollen anteriorly ; 



>rtnre contracted in the middle ; siphiincle siibcent ral ; septa 

 imple. concave. 



100 species. L. Silurian to Garb. Europe; N. America. 

 \. PYRIFORME. PL 97, fig. 489. Silurian. England. 

 \. BOHEMICUM, Barr. PL 97, fig. 490. Aperture. 



