258 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



This species diijfers from E. typus in having a shallower and more 

 rounded basin-shaped calyx, proportionally smaller basal, and larger 

 subradial pieces, and a more deeply impressed base. It very closely re- 

 sembles the Poterioerinus hemisphericus of Shnmard, examples of which 

 are associated with it in the collection. Indeed, so far as the character- 

 istics of the calyx alone are concerned, there appears to be no essential 

 difference except in the relative position of the small anal piece. In 

 Erisocrinus no anal piece is recognized as entering into the strnctnre of 

 the calyx, at least none that is visible upon the outer surface, as a 

 greater or less number of such pieces do in Cyatliocrinus and Poterio- 

 erinus, but I am not without suspicion that this form which I have, 

 according to the recognized usage in the limitation of genera, here 

 described as new, really belongs to the same species with P. Jiemiapheri- 

 eus, Shumard, and that the displacement of the small anal piece from 

 the rim of the calyx is an individual variation only. If this should 

 prove to be the case it is clear that a revision of the generic formula of 

 Erisocrinus will be necessary ; ' and it will doubtless also be necessary to 

 assign the type of this proposed species to P. hemisphericus, Shumard. 

 It is clear tliat the last-named species does not strictly belong to either 

 Poterioerinus or Ci/athoorinus, but it is not my purpose to discuss the 

 generic relations of these forms at this time. Figure 8, plate 1, repre- 

 sents an example of the P. hemisphericus of Shumard, which is introduced 

 for comparison with those of E. planus. 



Position and locality. — Upper Coal Measures, thirty miles west of 

 Humboldt, Kansas. See introductory remarks. 



Genus Cyathocrinus, Miller. 



Cyathocrinus stillativus (sp. uov. ). Plate 1, figs. 9 and 10. 



Body below the upper border of the first radial pieces shallow basin- 

 shaped, much wider than high, having a narrow, moderately deep, 

 abrupt, five-sided depression at the center of the base, at the bottom of 

 which is the facet for the attachment of the column; composed of 

 eighteen moderately thick and strong pieces, all of which, except the 

 basals, are more or less tumid in their middle portion, some of them 

 presenting an irregular, uneven surface, which, with the impressed 

 sutures and the still more deeply impressed corners of the pieces, gives 

 the surface of the body a decidedly rugose aspect ; basal pieces very 

 small, occup^'ing the bottom of the depression at the base, the greater 

 part of each being covered by the first joint of the column; subradial 

 pieces having their height and width about equal, four of them pen- 

 tagonal, and one, that which is next below the first anal piece, hex- 

 agonal, there being no appreciable angle upon that side of any of them 

 which adjoins the basal pieces; first radial pieces much larger than the 

 subradial, wider than their fuU height including the arm facet ; the two 



