HURONTA, AULACOCERAS, ETC. :209 



Ormoceras, Stokes. 



Siphuncular beads constricted in the middle, so that the septa 

 appear us if united to the centre of each. Probably identical 

 with Actinoceras. 



Three s[ccics. L. Silurian 1o Devonian. N. America. 



(). P>AYKIKM)I. Stokes. PI. 9C>. fig. 47 C>. 



Huronia, Stokes. 



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

 large, central, upper portion of each joint inflated, connected 

 wiih a small ccniral lube by radiating plates. 



Three species. L. Silurian. Dnnnmond IsL, L. Huron. 



I'sually the siphuncle only is preserved. Dr. Bigsby obsei'ved 

 specimens six feet in length. Doubtfully distinct from Actino- 

 ceras. 

 H. VKRTKBRALTS. Stokes. PI. 9(1. fig. 477. 



Aulacoceras, Hauer. 



Shell much thiokenwl. longitudinally furrowed, with two deep 

 lateral sulcations ; si])hon vei'v small, marginal and dorsal. 



Four specie's. Tpper Triassic. Austria. 

 A. siiM'ATUM, Hauer. PI. 9(J. fig. 478. 



Bathmoceras, Barnin lc. 



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

 creasing in horizontal extension from below upwards ; siphuncle 

 a series of superimposed funnel-shaped tubes. 



Two species. Middle Silurian. Bohemia. 



Endoceras, Hall. 



Shell extremely elongated, cylindrical. Siphuncle very large, 

 cylindrical, lateral; thickened internally by repealed layers of 

 shell, or partitioned off by funnel-shaped diaphragms. 



Twelve species. L. Silurian. New York. 

 KNDOOERAS. Ideal section. PL %, tig. 479. 



E. PROTEIFORME, Hall. PI. 9C>. tig. 480. 



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