222 



Cincinnati Society of Natural History. 



was attached. The stalk rises from the central depressed area, and 

 consists, at first, of interlocking plates, but afterward, of circular 

 ones, like those of a crinoid column, and finally tapers to a point. It 

 was flexible and perforated with a longitudinal channel, though the 

 perforation has not been satisfactorily ascertained, at the upper ter" 

 minating point. 



Order Myelodactyloidea, n. ord. 



This division of the fossil Echinodermata is established as follows: 

 Body free, discoidal, and possessed of an internal radiating system 

 of pores, which increase, by division, from the center to a tubular 

 channel in the circular margin or surrounding coil. There are two 

 families referred to this order, the ^Jvelodactylidae and the Cyclocys- 

 toididae. In the former, the radiating and circular systems become 

 complicated by the connection, between succeeding coils and through 

 the flattened connecting finger-like processes; in the latter, the arrange- 

 ment is more simple, as the interior radiations connect with a single 

 marginal circular S3 r stem. The external form and internal structure 

 are so essential^ distinct from other well defined orders, that the 

 technical names, used in description, have no ascertained application. 

 That is, we can not intelligently apply the words calyx, ambulacra, 

 arm, etc., to any part of these peculiar organisms. This order has 

 been suggested with hesitation, because there still exists a possibility 

 that Myelodaetylus belongs, in some manner, to the vault of a crinoid, 

 but the author thinks there is not much probability of such connection. 



Family Myelodactylid^e, n. fam. 



This family is founded upon the single genus ATyelodactylus, and 

 defined as follows: 



Bod}- free, discoidal, and resembling a coil rolled in the same plane, 

 and covered upon either side b} T finger like processes from each 

 succeeding turn overlapping the next inner one. The whorls are 

 composed of a series of plates, having a tubular channel within, and 

 perforated and finger-like processes upon the exterior, directed toward 

 the center, and flattened down upon the next inner whorl to which they 

 are attached, and form a porous connection from the tubular channel 

 of one whorl to the next inner one. The cast of the pores of the 

 inner whorl resemble the radiating spokes of a wheel: they are multi- 

 plied in connecting the tubular channels of each succeeding whorl, 

 thus making the internal radiating system doubly complicated. The 



