294 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



always more or less excentric. Neither can the presence or absence of inter- 

 distichals, unless accompanied by other distinctive characters, be considered 

 sufficient for generic separation, as proposed in the case of Cteiiocrinus 

 Bronn.* Those plates are mere auxiliary pieces, which may be present 

 or absent in the same species. 



Turhinocnnites Troost was proposed in MS., according to Hall,t for a 

 species which was said to have the first anal plate on a level with the 

 radials ; but Troost's typical species, Melocrinus Veriieuili, had no such plate, 

 or Hall could not have stated that the anal area was but slightly distinct 

 from the other four. 



Cytocrinus was described by Eoemer with three (?) basal plates — the 

 exact number not having been ascertained. A good specimen in our collec- 

 tion from Roemer's typical locality plainly shows four plates, and we have 

 no doubt the species is a Melocrmus. 



PhUlipsocrinus McCoy is described with four basals, succeeded by seven 

 plates in the next ring, which shows that it is an abnormal specimen. If it 

 is, as we think, an Actinocrinoid, the abnormal seventh plate may have 

 necessitated the presence of a fourth basal. 



In addition to the species herein figured and described, we note the 

 following : Melomnus obpyramidalis Winchell and Marcy, M. VerneuUi Hall 

 (not Oehlert), and M. nodosus Hall, which were described from unsatisfactory 

 natural casts. Neither can M. Pratteni {Forhesiocrinus Pratteni) McChesney, 

 which was defined from a fragmentary specimen, or Melocrmus sculptus Hall, 

 of which only the basal plates are known, or M. IrevidadyluB Hall, which 

 was figured but not described, and the figure not properly published, be 

 regarded as good species. 



* The genus Gtenocrinus was at first incorrectly defined. It was described by Bronn, 1840 (Jahrbuch, 

 p. 542), witli three basal plates, and this number was confirmed by Roemer (Lethaea Geogn., 1855, p. 251). 

 Subsequently de Koninck considered the genus identical with Pradocrinus De Verneuil, which actually has 

 three basals. Joh. Miiller (Verhandl. naturh. Verein, 1855) admits more than three basals, probably five, 

 and in 1857 (Neue Echinod. Eifl. Kalk., p. 255), asserts positively the presence of five basals. He com- 

 pared Ctemcrinus with Gl^ptocrinus Hall, and supposed both to have " parabasalia." Schultze afterwards, in 

 his Monograph, p. 63, proved from more perfect specimens that Gtenocrinus typus has \)w.ifour basals, and no 

 infrabasals, and referred that species to Melocrinus. Eollman, in his article on the " Unterdevonischen 

 Crinoideen," Verhandl. Naturh. Verein, 1887 (private ed., p. 14), revised the genus Gtenocrinus with four 

 basals, but pointed out no characters by which it may be distinguished from Melocrinus. 



t 28th Rep. N. Y. State Mus. Nat. Hist. (Museum edit.), p. 139. 



