240 PROCEEDINGS OF THE ACADEMY OF [1881. 



1870. Zittel. Handb. d, Palseontologie, p. 364. 



Not Phill., 1841. Pal. Foss. Cornwall, p. 28. = Hexacrinus. 



Not F. Roemer, 1844. Rliein. Ueberg. Geb., p. 63. = Coccocrinus. 



Not D'Orbigny, 1850. Prodr. d. Pal., i, p. 103. = Hexacrinus. 



Not F. Roemer, 1851. Foss. West Tenn., p. 35. = Marsupio- 

 crinus. 



Not Hall, 1861. Pal. N. York, iii, p. 113. = Cordylocrinus and 

 Marsiqnocrin us. 



Not Schultze, 1866. Ecliin, Eifl., p. 68. = Storthingocrinus. 



Not Lyon, 1869. Am. Phil. Soc, xiii, p. 459. = Hexacrinus. 

 Syn. Astropodia Ure., 1797. Hist, of Rutherglen. 

 Syn. Nave Encrinite Parkinson, 1811. Org. Rem., vol. ii. 

 Syn. Encrinites Schlottheim, 1823. Nachtr. Petrefaktenk. 

 Syn. Gentrocrinns Austin, 1843. Rec. and Foss. Crin., p. 6 

 Syn. Pleurocrinus Austin, 1843. Rec. and Foss. Crin., p. 6. 

 Syn. Edzoardsocrimts D'Orbigny, 1850. Prodr. d. Paleont, i, p. 156. 

 Syn. Edwardsocrinvs D'Orbigny, 1852. Cours. Elem., ii, p. 145. 

 Syn. Edwardsocrinus Pictet, 1857. Traite de Pal., iv, p. 331. 



Platycrinus was correctly defined b}' Miller, and his original 

 species with the single exception of PI. pentangularis, have been 

 retained in the genus ever since. This species, described from an 

 imperfect specimen, was made b}' D'Orbigny the type of his 

 genus Dimorphocrinus (Prodr., i, p. 155), but is evidently a 

 Pentremites. 



Austin supposed the basal disk to be undivided in Platycrinus^ 

 and admitted into it species whicli have a large anal plate in line 

 with the first radials, but such only in which he thouglit the base 

 to be composed of a single piece ; he refers all species, in which 

 he had " observed a tripartite base," to his genus Hexacrinus, 

 whether they have an anal plate or not. 



The several species which Gold fuss placed under Platycrinus 

 embrace very diflferent forms, only comparatively few of which 

 can be retained, and some of them must be arranged under dis- 

 tinct families. 



Phillips' two species, from the Devonian of Cornwall, have been 

 placed with Devonian species from other localities under Hexa- 

 crinus. 



Roemer's Platycrinus rosaceus is a Coccocrinus, his P. Tennes- 

 seensis, and Hall's P. tentaculatus, both from the Upper Silurian, 

 have been referred by us to Marsupiocrinus ; Hall's P. parvus, 

 P. plumosus and P. ramulosus to Cordylocrinus. 



Schultze, in 1866, described under Platycrimis several species 



