252 Cincinnati Society of Natural History. 



Graphiocrinus, Korninck k Le lion Cromyocrinus, Trautschold. Eupachycrinus, M. & AY. 



Under basals five. Under basals five. Under basals five. 



Basals five. Basals five. Basals five. 



Radials five. Radials five. Radials five. 



Brachials five. Brachials five. Brachials five. 



" Anal" one. " Anals" three or more. " Anals" three, rarely 1. 



The most hasty A'iew of these tables shows that the generic differ- 

 ences, if such exist, must be found in the " anal" plates, or in some 

 portion of the specimens not embraced in the formulae. 



According to figures and descriptions of these genera, and of species 

 referred to them, Graphiocrinus has a single row of arm plates, and 

 ten arms. Cromyocrinus, single rows of arm plates, and either five or 

 ten arms. Eupachycrinus.^ single or double rows of arm plates, or ac- 

 cording to "Wachsmuth and Springer, a mixture of these characters in 

 the same specimen, and the arms varying in number, according to ex- 

 amples in my collection, from five to fourteen; specimens having seven 

 and nine arms not being uncommon. 



It seems clear that a student of these species will find himself in a 

 state of inextricable confusion, unless this matter shall be adjusted b}' 

 referring these specimens to a definite place under the difi"erent genera 

 as defined. As our authors have made the genus Graiihiocrinus to in- 

 clude those species of this group with a single " anal" plate, and with 

 ten arms, composed of a single row of arm plates, we may leave this 

 genus out of the discussion, believing that it will include, with the 

 proviso that a single " anal" shall not be held as generic in this case if 

 not in others, a well-defined group of species, of which the GrapJiio- 

 crinus encrino ides is the type. 



As regards the genus Croniyocrimis, which was correctly defined b}^ 

 its author, it seems well fitted to embrace all those species having three 

 or more "anals,'' a body composed of comparatively' heavy convex 

 plates, and five or ten arms made up of single rows of plates as in 

 Graphiocrinus. If the genus Eupachycrinus can be regarded as 

 "established," it should be made to include those species of this group 

 having one or more " anals," heavy rounded body- plates, and ten to 

 fourteen arms, with double series of interlocking plates. 



It is certainly a curious statement that a character may be generic 

 in one case, and only specific in another, from the same group of cri- 

 noids, of precisely the same geological age, surrounded b}- the same 

 environments, and left as a fossil not only in the same strata but in 

 the same layers. 



The so-called " anal plates," as I am satisfied after a verN' careful 

 study of numerous-sliced specimens, from many distinct genera, were 

 in no case in such relation to the other plates as to be of a valvular 



