60 



slightly on the loft and t!]e other broadly on the right and is 

 followed by a longitudinal series of six or seven plates as dis 

 closed between the arms, and, on the right of this series, and 

 sejiaratcd from it by a nearly straight suture, there is a longi- 

 tudinal series of seven plates; on the left and sei)aratt.'d by a 

 longitudinal suture there are nine plates iu a double series, 

 arranged with some irregularity. There are, therefore, as many 

 as tiWentytive or twenty-six plates in this area. 11 will be seen 

 that if the distinction between Taxocrinus and Furbesocriiius is 

 (lei)('ndent upon the azygous area that we have here a Tarn 

 rrivKS by reason of the longitudinal seri<^s of |ilali's, and a 

 Forbesocrmus by reason of the large area. 



This species will be readily distinguished by its (|uiii(|uelobato 

 loi-iii, number of primary and .secondary radials and shapi; of 

 tlie interradial areas and by the azygous plates. 



Found by the late Wm. McAdams, in whose honor the speci- 

 tic name is given, in the Keokuk Group, in Jersey county, Illi- 

 nois, and now in the collection of Wm. F. E. Gurley. 



Family PLATYCRINID/E. 



PLATYCKINITS FOKMOSUS, var.. Ari'KOXlMATl s, n. var. 



Phife IV, Fig. 8, basal view; Fig. '.), suiiimH view; Fig. UK 

 azygona side view: Fig. 11, opixisHeside. 



This species or variety is medium size and belongs to the 

 discoid forms. It is so nnicli like P. formosus that it can only 

 be cuIIimI a variety, in the absence of a Ixuowledge of the vault 

 of tijuit species, and, if the vaults are alikt; then the varietal 

 name may be stricken out. but if the vaults are dilTi-rently 

 constructed then the varietal naine may liavr the i-ank of a 

 species. The calyx is shallow, though deeper than in tie 

 types of /-*. formosus, pentagonal, three times as wide as high. 

 Plates thick and beai'ing low rounded nodes less conspicuous 

 than they are in the types of P. foriiin.'<ii,<. Sutui'es beveled but 

 n(;t canaliculate as they are in /'. formosu.^. 



Hasals form a concave pentagonal disc bordered by a nodose 

 rim. The first radials are rounded upward from the basal 

 suture and constricted in the middle part, beyond which they 

 are directed horizontally, and the facet for the second plate is 



