792 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 thereception 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 Locahty. — Lower Chemung group; Steuben Co., N. Y. 
Types in the collection of Wachsmuth and Springer. 
fiemarks. — This species is known only from natural moulds and gutta 
percha casts. We had 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 puncto- 
brachiata 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. 
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