nS PROCEEDINGS OF THE ACADEMY OP [1886. 



We are not satisfied whether the piece resting upon the radials 

 (White's fig., 5 a) is equivalent to the one between the radials (his 

 fig., 5 c), it is at least possible that the former is the anal plate, 

 the latter a plate of the tube, or, as it is generally called, the third 

 anal plate. We, therefore, cannot agree AA^ith White in consider- 

 ing the two forms generically identical, and much less specifically. 

 If the difference in the two specimens was to be explained by 

 individual development, that perhaps the anal piece had been 

 resorbed in the adult, the specimens should differ in size, which 

 is not the case. Throughout the coal-measures we find both 

 forms side by side and of nearly equal size, a certain proof that 

 the modification took place in the genus, and not in the individual. 

 We must therefore either separate the two forms generically, or 

 unite both with Eupachycrinus. 



We stated under Eupachycrinus that we separate from that 

 genus all species with a single azygous plate, and these we place 

 under Geriocrinus. Contrary to White, however, we exclude 

 those species in which that plate rests upon the radials, which we 

 place under Erisocrinus. Whether EiHsocrinus and Geriocrinus 

 are full genera or only subgenera of Eupachycrinus^ or the latter 

 two of Erisocrinus^ is a question which we leave open. 



Geriocrinus occupies the same relative position to Graphio- 

 crinus as Zeacrinus to Woodocrinus, and as Eupachycrinus to 

 Scytalocrinus, their differences being more of degree than of kind. 



We refer to Geriocrinus the following species : 



*]875. C. Craigii (Worthcn), Eupachycrinus Craigii, Rev. i, p. 138. 



*1S73. C. fayettensis (Wortlien), Eupachycrinus fayettensis, Rev. i, p. 138. 

 1866. C. inflexus (Geinitz), Cyathocrinus inflexus, Carbon, and Dj-as in Nebraska, 

 p. 62, PI. i, fig. 20; White, 1876, Scaphiocrinus carbonarius (not M. and 

 W.). Powell's Rep. Geol. Uinta Mts., p. 89; AVhite 1880, Geriocrinus 

 inflexus, 12th Ann. Rep. Terr., by Hayden for 1878 (author's ed., p. 127). 

 Carboniferous. Grand and Green River. Utah and Nebraska. 



*1858. C. hemisphericus (Shum.), Scaphiocrinus (?) hemisphericus, Trans. St. 

 Louis Acad. Sci., vol. i, p. 221. Meek 1872, Final Rep. on Nebraska, p. 

 147, PI. 5, Fig. 4, and PI. 7, fig. 1 ; also Geol. Rep. 111., iii, p. 561, PI. 24, fig. 

 6. Carboniferous. This species we took (Rev. i, p. 138) to be a synonym 

 of Eupachycrinus Craigii, but, if Meek's identification is correct, it is a 

 good species. The plates, which in the latter are strongly spiniferous, are 

 in the other but little convex. 

 1880. C. planus (White), Erisocrinus planus (Type of the genus), Proc. U. S. Nat. 

 Mus., vol. ii, p. 257, figs. 6-7. White 1880, Erisocrinus (Geriocrinus) 

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

 PI. 35, fig. 5 c (not 5 a = Erisocrinus White). Coal measures. Humbold 

 River, Ky. 



