406 PALAEONTOLOGY OP ILLINOIS. 



more than half as wide as the body, below; apparently some- 

 what thicker above. Body plates not convex, but merely 

 granular, and joined by close-fitting sutures. Column 

 slender, round, and composed of nearly equally moderately 

 thick pieces, near the base. 



Hight to top of first radial pieces, about 0.15 inch; 

 breadth, 0.24 inch ; length of arms, about 0,95 inch. 



This is one of those few intermediate types such as we occasionally 

 meet with in various departments of Natural History, when extensive 

 collections can be studied connecting, or standing, as it were, inter- 

 mediate between two genera. That is to say, it combines some of the 

 characters usually regarded as belonging especially to Poteriocrinites, 

 with others equally characteristic of Cyathocrinites. Its body has much 

 the usual form of Cyathocrinites, with the double alternating series of 

 anal pieces precisely as we see in Poteriocrinites. On the other hand, it 

 has the narrow, decidedly lateral proboscidiform ventral extension of 

 Cyathocrinites, and might, with almost equal propriety, as far as we yet 

 know, be called Cyathocrinites f perplexus. The existence of such a type 

 would, in the estimation of some naturalists, be regarded as a sufficient 

 reason for uniting the genera Poteriocrinites and Cyathocrinites. In this 

 opinion, however, we cannot concur, for we believe that if all the genera 

 thus connected by a few obscure forms were united, it would be found 

 impossible to fix any limits whatever to such groups, with all the extinct 

 types before us. Possibly characters may be found, however, warrant- 

 ing the establishment of a new genus for such forms. 



Specifically, this little Criuoid seems to be most nearly allied to our 

 Cyathocrimis ? enormis, but it differs in the number and arrangement 

 of its anal pieces, as well as in having its arm pieces scarcely one-half 

 as long in proportion to thickness. 



Locality and position Lower part Burlington group of the Lower 

 Carboniferous, Burlington, Iowa. No. 264 of Mr. WACHSMUTH'S col- 

 lection. 



