6 BULLETIN 115, UNITED STATES NATIONAL MUSEUM. 



rcst'iubics the condition of the aduh coniatuhds generally, in which 

 the base is only a platform for the support of the visceral mass, in 

 contrast to the typical plan of the crinoids, in which the dorsal 

 parts iorm a cup inclosing the viscera. Among the paleozoic crinoids 

 of other Camerate families some exceptionally took the same form, 

 as, for example, the genera Agaricocrintis, Awpliora^'riniis, Cypho- 

 crinus, and the discoid species of Platycrinvs. 



The genus is represented by at least two species, one from the 

 Onondaga and one from the Hamilton. The Hamilton form was 

 described by Miller and Gurley as Stereocrinus indianensis ,^ with 

 little indication of its peculiar characters, although they noted that 

 the species bears little or no resemblance to the type, and referred it 

 to Stereocrinus only because of its supposed identity under the generic 

 formula of 'two primary radials"^ — that is, only one primibrach. 

 Even this was incorrect observation, the authors failing to see the 

 reduced first primibrach, which is constant in all specimens in which 

 the plates can be distinguished. Their type was from the Louisville 

 area, where a number of specimens preserving the tegmen have 

 been found. Specimens of what may be the same species occur in 

 the Hamilton of western New York, in one of which the character 

 of the uniserial arms is well shown. 



The Onondaga species is much larger. Specimens from the Falls 

 of the Ohio at Louisville show some structural details better than 

 the Hamilton form, especially the extreme of fixed pinnulation; but 

 the tegmen is not preserved. Therefore I take the S. indianensis 

 as the type of the genus, and for the Onondaga form I propose the 

 name Comanthocrinus priscus. The latter species also occurs in 

 western New York. 



Genotype.- — Stereocrinus indian£nsis Miller and Gurley. 



Distribution . — Middle Devonian: Louisville area and New York. 



COMANTHOCRINUS INDIANENSIS (Miller and Gurley). 



Plate 1. figs. 1-G. 



Stereucritius indianensis Miller and Gurley, Bulletin Xo. 12, Illinois State 

 Museum, 1897, p. 38, pi. 3, figs. 13-15.— Rowley in Greene, Contr. Ind. Pal., 

 1904, vol. 1, p. 182. pi. 54, figs. 7, 8. 



Type of the genus. The species is of relatively small size, average 

 specimens being about 20 mm. wide on the base and 17 mm. high 

 to the top of the tegmen. Dorsal cup low and flat; the relations of 

 its component plates are best shown by the accompanying generic 

 diagram (text fig. 1), composed upon the evidence of 12 specimens 

 of this species; the reduced and modified first primibrach is drawn 

 in its various forms in the different rays, also variations in the inter- 



Biill. No. 12, lU. St. Mus., 1897, p. 3S, pi. .■{, figs 13-1.5. 



