1879.] NATURAL SCIENCES OP PHILADELPHIA. 267 



anal nor interradial plates, while Forbesiocrinus had both, and 

 sometimes a large number of them. 



In 1866, both Meek & Worthen and Schultze wrote on this 

 subject, and arrived independently at the same conclusion. The 

 former, in an elaborate article in the Illinois Geological Report, 

 vol. ii. p. 270, show that the same species may have sometimes no 

 interradials, and again from one to three. They refer to Taxo- 

 crinus Hall's Foi^besiocrinus Thiemei, which was described as 

 having no interradials, but which has sometimes two, and which 

 we have even found with as many as five regular interradial plates. 

 The one, according to De Koninck, would be Taxocrinus, the 

 other Forbesiocrinus. To amend the generic formula so as to 

 admit species with one or two series of interradials, did not seem 

 to those authors expedient, since the species exhibit such a wide 

 range of variation in this character. Nor do they consider the 

 presence of axillaiy plates which occur in both groups, nor the 

 small patelliform supplementary pieces of some well-defined species 

 of Forbesiocrinus a means of distinction, inasmuch as they are not 

 always present in otherwise typical forms of that group ; while 

 well-marked species of Taxocrinus are described as showing the 

 patelloid plates between the arm joints. Meek and Worthen 

 therefore concluded, until more distinctive characters should be 

 discovered, to place Forbesiocrinus embracing species with many 

 interradial and anal plates as a mere section under Taxocrinus. 



Schultze found in his Devonian species almost every character 

 of Forbesiocrinus except the small patelloid plates, but whether 

 these were sufficient to distinguish it from Taxocrinus, he did not 

 wisli to decide, and so he placed the species from the Eifel, in 

 which these plates do not occur, .under Taxoci'inus. He, how- 

 ever, included with this genus species which evidently belong to 

 very distinct genera. 



Angelin, in the Iconographia Crinoideorum Suecias, pp. 8, 9, 

 gives generic descriptions both of Taxocrinus and Forbesiocrinus, 

 and ranges under the two genera several new species. His de- 

 scriptions only differ, so far as we understand them, in this : that 

 in Forbesiocrinus the number of primary radials is left an open 

 question, while in Taxocrinus the number is fixed at 3 X 5 ; that 

 the former had one large hexagonal anal plate (he evidently 

 meant, to judge from his figures, "and other smaller ones succeed- 

 ing"), and a considerable number of interradials, the lower one 



