HITKOMA. AIL ACOCKRAS, KTC. 209 



Ormoceras, Stokes. 



Siphuncular beads constricted in the middle, so that the septa 

 appear ;is if united to ihe centre of e:ich. Probably identical 

 with Actinoceras. 



Three species. L. Silnrirni to Devonian. .V. America. 

 (). BAYFIKUU. Stokes. PI. 90. fig. 47(5. 



Huronia, Stokes. 



Shell extremely thin, membranous or horny (!'). Siphuncle very 

 large, ceiiiral. upper portion of each joint inflated, connected 

 wi;h a small central tube, by radiating plates. 



Three species. L. Silurian. Drummond IsL. L. Huron. 



Tsnally the 1 siphuncle onl\ is presei'x'ed. I)r. IJigsbv observed 

 specimens six feet in length. Doubtfully distinct tVom Artino- 

 eeras. 



II. \ KKTKURALFS. Slokes. PI. 0,",. iio-. 477. 



Aulacoceras, I-lauer. 



Sliell much thickened, longitudinally furrowed, with two deep 

 lateral sulcations; siphon very small, marginal and dorsal. 

 Four species. Tpper Triassic. Austria. 

 SUtCATUM, Ilaiier. PL 90. lig. 478. 



Bathmoceras, Barran 1(>. 



Part of the body-chamber occupied by imbricating- plates, de- 

 reasing in hoi'i/ontal extension from below upwards; sipliuncle 

 series of superimposed funnel-shaped tubes, 

 'wo species. Middle Silurian. Bohemia. 



Endoceras, Hall. 



>hell extremely elongated, cylindrical. Siphnncle very large, 

 Lmdrical, lateral ; thickened internally by repeated layers of 



shell, or partitioned otf by funnel-shaped diaphragms. 

 Twelve species. L. Silurian. New York. 



KNDOCERAS. Ideal section. PI. !)0. fig. 4*79. 



E. PROTEIFORME, Hall. PL 90, fig. 480. 



27 



