Hl-RONTA, AHLAOOCKRAS, KTC. -JOy 



Ormoceras, Stokos. 



Siplmiicuhii' lu'iids const I'ictcd in tlic middle, so tluit tiie septa 

 ;i[)i)(';u- as if united lo liie centre ol" eacli. I'roitalily identical 

 with Ac/inocerns. 



Tiiree species. L. Siini'ian lo Devonian. N. Ami'rica. 

 (). P>AYKrF.M)T. Stokes. IM. ',)('). fiu'. 4Tr.. 



Huvoiiia, Stukcs. 



Sliell extremely tliin. meml)ranons or lioi'iiy {''). Sipiiuncle vei-y 

 large, central. ui)per portion of eacli joint inflated, connected 

 with a small central tnhe \)\ railiating" plates. 



Tlii-ee s])ecies. L. Silnrian. Drummoud IsL. L. Huron. 



Usnally the sijjhuncle only is ])reserved. Dr. IJig'shy observed 

 specimens six feet in U'ngMi. Donlitfnlly distinct .from .4r/i//(<- 



H. VKR'rEHMArjs. Stokes. PI. 9i;. iig. 477. 



Aulacoceras, Hauer. 



Shell mnch thickened, longltndinally fnrrowed. with two deep 

 lateral sulcations ; siphon very small, marginal and dorsal. 



F'onr species. Upper Triassic. Audria. 

 A. sxiiA'ATUM, Ilaner. PI. 9(;. Iig. 478. 



Bathmoceras, Barvan Ic 



Part of the l)ody-chambei- ocenpied by imbricating lilates. de- 

 creasing in horizontal extension from l)elow npwai'ds ; siphiincle 

 a series of snperimposed funnel-shaped tubes. 



Two species. Middle Silurian. Bohemia. 



Endoceras, Hall. 



Shell extremely elongated, cylindrical. Siphuncle very large, 

 cylindrical, lateral ; thickened internally by repeated layers of 

 shell, or partitioned off by funnel-shaped diaphragms. 



Twelve species. L. Silurian. New York. 

 Endoceras. Ideal section. JM. l»(i, fig. 479. 

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



