150 Cincinnati Society of Natural History, 



Not less remarkable is a series of specimens, embracino- characters 

 belonging both to Hemicystites and Edr toaster. Of these curious fos- 

 sils there are a number of specimens, the consideration of which must 

 be left to a future paper. It is also a fact of especial significance, that 

 these strata have furnished several specimens of two species of 

 Archceocyathus, a genus not hitherto found outside of the Potsdam and 

 Calciferous. Indeed, the whole group of fossils here associated is of 

 such a high order of interest, that I feel certain m}^ fellow laborers 

 everywhere will be glad to know that they have been brought to light. 



Genus Hybocystites, Wetherby. 



Generic Description — General outline of the bodj^ very similar to 

 that of Hyhocrinus tumidus, Billings. It consists of series of plates, 

 five each in the first two, arranged as in Hybocrinus. As in that 

 genus the lower azygous plate bears a second and a radial upon its upper 

 face. Arms three, one upon each side of the upper az3^gous plate, and 

 one immediatel}' opposite it.* The plates of the upper series between 

 these arms, on either side, are excavated by a groove that is continued 

 downtvard, and half or two thirds across the plate of the lower series 

 beneath it. 



These grooves meet in the vault at a common point with those of the 

 arms, and form a part of the ambulacral sj^stem. 



The mouth, or ambulacral orifice, is situated nearly centrally upon 

 the upper surface. The valvular anal opening is placed between the 

 upper az3'gous plate and the mouth. The arms are deepl}' furrowed, the 

 grooves being covered in b}^ a series of cuneiform interlocking plates. 

 Pinnulae not observed. Proboscis or ventral sac indicated b}^ the 

 presence of the upper azygous plate. Column small, round, and 

 placed excentrically as in Hybocrinus. Vault covered by plates of 

 which the arrangement can not be determined. There are no evidences 

 of pectinated rhombs or poriferous plates. This genus combines, in a 

 remarkable degree, characters both of the Crinoids and C3''stids. 



Hybocystites problematicus, nov. sp. 



(Plate v., fig. 1, summit or vault;; la, lateral view; 15, azygous side ; le, opposite side; figs. 1 

 and la. two diameters; figs, lb and Ic, natural size.) 



Basals — Five, pentagonal, higher than wide, somewhat convex or 

 tumid in the center, nearly alike in shape and size, resembling, in these 

 particulars, those of Hyhocrinus tumidus, Billings. 



Radials — Five, four large, pentagonal, and alternating with the 



* These arms are the right and left posterior and the anterior of most authors. 



