752 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



plate, above which the arms are biserial and widely divergent. Whether 

 they branch again is not known. There is but one interbrachial at the four 

 regular sides, which is located within the dorsal cup ; it is wider than long, 

 very large, and extends to the full height of the distichals. The ventral 

 disk is quite low, and depressed in the central portions, the ambulacra con- 

 spicuously projecting, especially on approaching the arms. The posterior 

 area is wide, bulging, and composed of a great number of plates, which form 

 a large, rounded protuberance containing the anal opening, which is directed 

 upward and surrounded by very minute pieces. Orals arranged in the usual 

 way ; the posterior one large, its diameter shorter from the anterior to the 

 posterior side. The plates covering the food-grooves rather large ; consisting 

 of two rows of pieces alternately arranged. The sockets for the reception of 

 the spines rather irregularly distributed and far apart ; they are large and 

 circular, and have a shallow pit at the upper face. The form of the spines 

 is not known, but they were evidently large. 



Horizon and LoeuUty. — Lower Chemung group ; Steuben Co., N. Y. 



Tyixs in the collection of Wachsmuth and Springer. 



Bemarks. — This species is known only from natural moulds and gutta 

 percha casts. We liad for description two specimens, one showing the dorsal 

 cup, the other the ventral disk, both presented to us by Prof. J. M. Clarke 

 of Albany. The species is readily distinguished from Arthracantha jjuncto- 

 hracliiata Williams by the more depressed form of the calyx, the greater 

 width of the costals, the presence of but one interbrachial piece and the fact 

 that this is located almost entirely in the dorsal cup, and by the less number 

 and greater width of the spine-bearing sockets. 



