232 PROCEEDINGS OF THE ACADEMY OP [1881. 



with that of Rocmer, except that he separates Symbathocrinus and 

 adds Corthjlocrinus and Pterotocrinus which had been established 

 later. He also placed here Storthingocrinus which we propose to 

 transfer to the Sj-nibathocrinidaj. 



The Platycrinidse are first met with in the Upper Silurian, 

 whence they range to the close of the Subcarboniferous. 



We arrange the two sections as follows : — 



a. Platycrinites. 



1. Coccocrinus. 5. Platycrinua. 



2. Cordylocrinus. Subgenus Eucladocrinus. 



3. Culicocrinus. 6. Gotyledonocrinus. 



4. 3Iai'supiocrinus. 



b. Hexacrinites. 



7. Hixacrinus. 9. Talarocrinus. 



8. Dkliocrinus. 10. Pterotocrinus. 



a. Platycrinites. 



1. COCCOCRINUS Job. Muller. 



1855. Muller. Verh. Natuih. Verein Rheinl., xii, p. 20. 

 1860. F. Roemer. Foss. Fauna. Westlich. Tenn., p. 51. 

 1879. Zittel. Handb. d. Palaeont., i, p. 347. 



Syn. Platycrinus Roemer, 1844 (not Miller), Rhein. Uebergangsgeb., 

 p. 63. 



Muller proposed the genus Coccocrinus for a species which had 

 previousl}^ been referred by Roemer to Platycrinus. The two 

 genera are identical in the construction of the calyx, and the 

 summit really forms the onl}^ distinction between them. In well- 

 preserved specimens of Coccocrinus^ the vault is constructed of 

 five large oral plates, which rest upon five interradial pieces. The 

 oral plates are not in contact laterally, but leave five slits, which 

 in the fossil have no floor nor covering, and leave an open space 

 in the centre. It is evident that the central space and open farrows 

 were covered in the animal as in similar genera, and this suggests 

 a closer analogy with Platycrinus than had been suspected by 

 Muller, Schultze, Zittel or Carpenter, who suggested an unob- 

 structed mouth. The interradial plate which rests upon the edge 

 of the first radials is characteristic of both genera, and the two 

 or more succeeding interradial dome pieces of Platycrinus are 

 possibly analogous with the single so-called oral plates of Cocco- 

 crinus. This, if correct, would reduce the generic diflference to 



