no PROCEEDINGS OP THE ACADEMY OP [1886. 



CROMYOCRINUS Trautschold. 



(Eeconstructecl W. and Sp.) 



1867. Trautschold, Crin. jiing. Bergkalk bei Moskau, p. 19. 

 1879. Trautschold, Monogr. Kalkbr. von Mjatschkowa, p. 117. 

 1879, Zittel, Handb. der Palseont., i, p. 360. 



Syn. Eupacliycrinus in part (W. and Sp.), Revision i, p. 133. 



Syn. Hydreionocrinus in part (De Koninck); Syn. Agassizocrinus in 



part (Worthen); Syn. Poterioerinus in part (McCoy), 



Placing Gromyocrinus as a synon^-m under Eupachycrinus, we 

 found it impossible to uphold the genus upon any of the charac- 

 ters that had been pointed out by Trautschold. Wetherby has 

 asserted (Journ. Cincin. Soc. IN^at. Hist., iir, p. 8), that the genus 

 was " well fitted to embrace all those species having three or more 

 anals, a body composed of comparatively heavj^, convex plates, 

 and ten arms composed of a single row of joints," He further 

 proposed to refer to Eupachycrinus all those species of this 

 group having one or more anals, heavy rounded calj^x plates, ten 

 to fourteen arms, and these composed of a double series of inter- 

 locking plates. The biserial arm structure, which is only a higher 

 form of the uniserial one, is as closely intermingled with the latter 

 in the Russian form as in the typical Eupachycrinus, and also 

 the plates of the calyx are heavy and convex in both groups. 

 The only distinction of Wetherby upon which perhaps a separa- 

 tion of the species referred by us to Eupachycrinus might be 

 established, is the number of azygous plates. We can separate 

 the species with a single plate from those with three pieces, as 

 proposed by White. A division of this kind, however, does not 

 in the least affect Gromyocrinus^yfYaoh, like the typical Eupachy- 

 crinus, has three azj^gous plates. But Gromyocrinus differs from 

 the typical form of Eupachycrinus, in the form of the calyx, the 

 relative size of the various plates, and in their mode of union. 

 In all American species of Eupachycrinus, the form is de- 

 pressed, more or less saucer-shaped, and the underbasals, which 

 are very small and totally covered by the column, rest within a 

 deep concavity together with the lower portions of the basals. 

 The latter plates, and also the radials, are comparatively large, 

 the underbasals small. In Gromyocrinus the calyx is globular, 

 constricted at the upper "end, the underbasals large, extending 

 conspicuously beyond the column and forming a shallow cup. 



