1881.] NATURAL SCIENCES OF PHILADELPHIA. 237 



1879. Zittel. Handb. der Paljeont., p. 365. 



Syn. Platycrinus F. Roemer, 1860. Silur. Faun. W. Tenn., p. 35. 

 " Cupellmcrinus Troost, 1850. List. Crin. Tenn.. p. 61 ; also 

 Shumard, 1866. Catal. Pal. Foss. North Amer., p. 361. 



Marsupiocrinus has undoubtedly close affinities with Platy- 

 crinus^ with which it has been identified by Joh. Miiller and Hall, 

 but it diftei's in the higlier orders of radials, which, instead of 

 being extended into free rays, form a part of the calyx ; and also 

 in having the column round instead of elliptic, and the canal 

 larger. 



Troost 's genus CupeUsecrinus, which was defined as late as 1866 

 by Shumard, must be considered a synonym of this genus, unless 

 it should hereafter be found that the anus in the former consists 

 of a simple opening through the vault, and not a tube as in the 

 latter, in which case a subgeneric division might be justified. 

 Troost, in his List. Crin. Tenn., mentions several species imder 

 Cupelldecrinus, one of which is probably identical with Roemer's 

 PL Tennesseensis, but none of them have ever been described or 

 figured. 



Angelin's Marsiqnocrinus dubiiis is quite a difierent thing, 

 probably an Actinocrinoid, as is indicated by the basal disk, 

 which, instead of being pentagonal, is hexagonal and divided into 

 three equal pieces. 



Joh. Miiller considered M. coelatus a Platycrinus (Monatsb. 

 Berl. Acad., 1841, p. 201), differing from the Austins, who made it 

 the type of a separate family in which they included the genus 

 Grotalocrinus. Pictet, Angelin, and Zittel view the matter as we 

 do, and place it as a distinct genus. under the Platj'crinidse. 



Generic Diagnosis. — Bod}' globular; calyx low, basin-shaped, 

 the lower portions flat or slightly convex ; sides more or less 

 straight, surface corrugated or ornamented by fine striations ; 

 symmetry perfectly pentahedral ; secondary and tertiary radials 

 forming part of the calyx ; connected laterally by a single inter- 

 radial plate. 



Basals three, large, unequal, arranged as in Platycrinus. 

 Radials 2X5; those of the first row large, meeting laterally, bent 

 abruptly from their connection with the basals, and forming with 

 them a shallow cup, the middle of their upper margins excavated 

 for the reception of a small triangular second radial, which is at 

 least as high as wide, but often higher, and which has convex 



