TKENTON FOSSILS. 



291 



S. Prof undo, (Hall), has been found at Isle La Motte in the Black Kiver limestone. It is obliquely 

 turbinate, often slightly curved near the base, expanding above more or less abruptly; cell profoundly deep, 



Fio. 190. 



Fio. 191. 



Stromatocerium rugosum. 



extending nearly to the base of the coral; margin of the cup reflexed; surface scarcely marked by transverse 

 rugfo ; lamillae from 36 to 80 strong, nearly equal on the margin, but distinctly alternating in length 

 within; no transverse dissepiments or celluliferous structure. This species is figured in first volume of the 

 Paleontology of New York, Plate XII, Figs. 4 to 4e. 



Streptelasma corniculum (Hall.) This species has been found in the Black Kiver limestone upon the 

 island in Button Bay. It is described in the New York Keports, as occurring only in the Trenton lime- 

 stone. This coral is turbinate, curved near the base, which terminates in an acute point, some- 

 what rapidly expanding above ; cup profound ; lamellas about sixty ; surface marked by strong 

 longitudinal lines indicating the lamellfe, which are crossed by fine concentric wrinkled lines. 

 Its length varies from three-fourths to one and half inches. 



Fig. 191 represents a small and nearly perfect specimen of the Streptelasma corniculum. 

 Graptolithus amplexicaule (Hall). The affinities of the graptolitida? are treated of elsewhere 

 in this Report. This is the only species of graptolite that occurs in the Trenton limestone. g 

 Only fragments of it have been found, which appear to have considerable thickness. The stipes comicnium. 

 are slender, linear, elongated, surrounded by small sheathing folioles or scales, giving it a serrated appear- 

 ance ; folioles small and acute. 



Fig. 192 represents several fragments of the G. amplexicaule, in a fragment of limestone. All the stipes 

 except one have been broken off by a fracture of the stone. 



Crinoidea. Numerous fragments of crinoidal stems are found in the Trenton limestone in 

 Vermont, but it has been impossible to identify most of the fragments with any known species. 

 A species of Schizocrinus has, however, been found in the Champlain Valley, and therefore we 

 add a description of it. Most of the crinoidal fragments found in this rock in Vermont, belong 

 probably to this genus. The pelvis of the genus Schirocrinus is composed of five pentagonal 

 plates; first costals five, joining at their lateral edges; second costals five, separated by a hexa- 

 gonal intercostal plate, which rests upon the upper lateral edges of the lower costals; scapular 

 and armplates five, hexagonal, the lower side curved and fitting the concave upper edge of the 

 plates below; hand joint double or bipartite, as also the interscapular, or interbrachial plates- 

 hands and fingers regularly bifurcating. 



The Schizocrinus nodatus (Hall), has its body cup-shaped, obtusely pentagonal, spreading 



Fio. 192. 



firaptolithus. 



somewhat abruptly from the body; arms short; fingers in ten pairs, fimbriated; column round? 



