1886.] NATURAL SCIENCES OP PHILADELPHIA. 179 



c. Erisocrinites. 

 ERISOCRINUS Rev. i, p. 1:^9. 



Admitting Geriocrinus^ we place under Erisocrinus all species 

 in which no azygous plates are represented at the dorsal side, 

 but we also include those in which a plate of the ventral tube 

 rests upon the radials. In all probability was the latter piece 

 always present in this genus. The structure of the arms is the 

 same as in Encrinus and Eupacliycrinus. 



The only new species to be added in the list is : 



*18S0. Erisocrinus Whitei W. and Sp., Erisocrinus (Ceriocrinus) planus (in part). 

 White 12th Ann. Rep. Terr, by Hayden for 1878 (Author's copy, p. 127, PI. 

 35, Fig, 5a (not 5c = Ceriocrinus planus). Distinguishing the specimen Fig. 

 5c specifically, we projiose the above name for the other to avoid confusion. 



STEMMATOCRINUS Trautschold, Rev. i, p. 141. , 



In Part I, we separated Stemmatocrinus from. Erisocrinus only 

 subgenerically, from the fact that it agrees with that genus in all 

 its particulars, except that the underbasals consist of a single 

 plate instead of five in the other, which we explained by anchy- 

 losis. This explanation was doubted by Carpenter, who in the 

 Chall. Rep., p. 152, says : " the plate in question appears to me 

 much more truly represented by the central pentagonal piece on 

 which the basals rest, and it is obviously what Schultze calls 

 ' eine fiinfseitige aus der Erweiteruug des obersten Siiulen- 

 gliedes gebildete Platte.' " And again : " the analogue of the 

 development of the other calyx plates indicates that they (the 

 underbasals) are primitively five separate plates like their homo- 

 logues in the apical system of Ophiurids and starfishes ; and a 

 theory which would homologize them with a plate that first 

 appears as a simple ring seems to me to run counter all true 

 notions of morphology." We confess that we do not understand 

 Carpenter's argument, for we believe Stemmatocrinus had primi- 

 tively five plates, which were united by anchylosis leaving no 

 vestige of the sutures. Similar cases of anchylosis among basals 

 and underbasals have been observed among other Palaeocrinoidea 

 and even among Neocrinoidea. In one of the two species of the 

 recent genus Bhizocrinus, the basals are distinctly divided, in the 

 other united by anchylosis. In Platycrinus it is absolutely impos- 

 sible to discover a suture between the basals, the anchylosis 

 between the plates is complete, and only in comparatively few 



