SUPPLEMENTARY NOTES AND OBSERVATIONS. 391 



distinct from those of Megistocrinus, and which, so far as known, are of 

 Silurian age. 



Megistocrinus marcouamts^ W. and M., is Saccocrinus christyi, Hall = 

 Acfinocriiius whitjieldi* An examination of the figure, and a subsequent 

 examination of a specimen thus labelled in Prof. Marcy's collection, and 

 which appears to have been the original of the figure given, leaves no 

 doubt regarding the identity. The bifurcations of the rays take place in 

 precisely the same manner in the two individuals; and differences as great 

 as those indicated, in the plates and form of the body, can be detected 

 between many of the individuals from Waldron, and are of no specific impor- 

 tance. Prof. W. points out a difference in the number of interradial plates, 

 stating that they are always less than fifteen. Now there are only two of the 

 interradial areas of his specimen showing plates, and either of them will 

 show fifteen plates, or even more than this number, counting the smaller 

 ones in the upper part of the area. In one of the areas, sixteen plates can 

 be distinctly counted. From the concluding paragraph of the description, 

 one might infer that he is not aware that the formula of the Grenus Megis- 

 tocrinus is the same as that of Actinocrinus. There was no necessity' 

 for feeling ^''constrained to say,''^ what every one knew before. 



Megistocrinus infelix, W. and M., p. 110, is only a smaller individual of 

 the preceding species, possessing all the characters of the Waldron speci- 

 mens and none others. The number of interradial plates may appear less, 

 as those of the upper part of the area are too small to be counted in a 

 cast of the interior, especially since this cast is very indistinctly preserved 

 in some of its parts. The constrictions of the interradial and anal areas 

 between the arm-bases is a character common to all the Waldron speci- 

 mens, when preserving the margin of the dome. This feature is well shown 

 in Saccorimis speciosus^i figured by Rcemer. The bifurcation of the rays 

 takes place at the same height as in the Waldron species of the same 

 size ; the ridges along the radial series are subject to much variation, but 

 these differences are of no specific value. Both Prof. Winchell's figure 

 and specimen leave no doubt of the identity of this form with Saccocrinus 

 christyi, Hall. 



Megistocrinus necis, W. and M., pa. 110, in the smaller specimen, is 

 pentagonal at the base and constricted above. The specimen communicated 

 by Prof. WiNCHELL under this name appears to be the one given in out- 

 line, which I should regard as S. christyi with the summit unusually 

 constricted, but showing no marks of specific distinction. 



Ichthyocrinus corbis, W. and M., pa. 89, has already been noticed. The 

 diagram given cannot have been made from any specimen in the collection 



* There being already an Actinocrinus christyi, the Niagara species would be a syno- 

 nym, unlesss the Genus Saccocrinus be adopted. 



t The fossil referred by Dr. Rcemer to Saccocrinus speciosus is probably not of that 

 species, but more likely identical with the Waldron species. 



