WKITEAVES.J FOSSILS OF HAMILTON FOEMATION OF ONTARIO. 373 



Lyon and Casseday, and find that your specimens are young- specimens of 

 that species. All M. rngosus that I have seen have sixteen » rms. The 

 larger one you sent has sixteen arms, and the shape and ornamental mark- 

 ings are identical with the type specimens, although somewhat worn. The 

 markings on the smaller one are more distinct, but the basal plates do not 

 show so well as in the larger one. Both are true Meyisfocrinus rugosus. 

 I am obliged to you for sending these two crinoids, for I know now 

 that M. rugosus has an extended distribution." 



The original types of M. rugosus are from the " quarries at Bear Grass 

 Creek, near Louisville, Kentucky," though Clarke County, Indiana, is the 

 first locality indicated for this species by Waohsrauth and Springer (op. 

 cif., p. 543). 



Genn.eoceinus Arkonensis. (N. Sp.) 



Plate 48, figs. 7 and 7a, and the accompanying cut. 



\ > ^ oKo '" < if 



^ ^r) /-v w /-A rf 



Fig. 2. Gennaocrinus Arkonensis. Diagram of all the plates of the dorsal cup that are 

 visible in the specimen figured on Plate 48, with .some of those at the com- 

 mencement of the arms. Three tinjes the natural size. 



Calyx unusually small for the genus, the most perfect specimen known 

 (the one figured) being about ten millimetres in its maximum breadth, 

 though slightly and abnormally compressed, and a little broader than 

 high : arms very long in proportion to the size of the calyx, pinnules also 

 long, numerous and den.sely crowded. Dorsal cup semiglobose, cup- 

 shaped, widening gradually upward and widest above, its surface mark- 

 ings very faint and indistinctly defined. In the median line of the radial 

 and first costal each ray is marked by an obscure, low, rounded, longi- 

 tudinal ridge, which bifurcates in the upper portion of the second costal. 

 The surface of the lower and larger plates also, especially that of the 

 radials and first " interbrachials, ' is marked with six or seven obscure, 

 low, depressed-convex, radiating ridges near their outer margin, the 

 central portion being entire and either smooth or occasionally bearing a 



