1886.] NATURAL SCIENCES OP PHILADELPHIA. 85 



liim that Haplocrinus is a persistent larval form, but do not 

 understand how the five large plates, which occupy almost the 

 entire ventral surface, and as much as one-half of the whole test, 

 possibly can represent the orals in a Paloeocrinoid, as all other 

 genera of this group in which the ventral covering has been 

 observed, have largely developed interradials, and these, whether 

 composed of one or a series of plates, extend up invariably to a 

 comparatively small area surrounding the peristome. We, there- 

 fore, regard the small central piece as the homologue of the orals, 

 and not the five large plates which we take to be interradials. 



The basals of Haplocrinus were described by Dujardin and 

 Hupe to be composed of three pieces in place of five. The three 

 small plates alternating with the basals, the " Costalglieder " of 

 Roemer, which are radial in position and support three of the 

 arm-bearing plates, were called b^' Schultze " parabasalia," by De 

 Koninck " subradials," while Miiller, Pictet and Zittel called them 

 "first radial plates." The term parabasals was used by Schultze 

 for basals in dicyclic Crinoids, and, therefore, cannot be applied 

 to radial plates, neither can the name " subradials," as also this 

 term has been used in the same sense. We regard the three plates 

 as representing mere sections of the radials, which, jointly with 

 the arm-bearing part above, are equivalent to one of the undi- 

 vided radials of the other two rays. 



Generic Diagnosis Of very small size. Form of calyx sub- 

 globose, sometimes biturbinate, extending almost over the whole 

 A^entral surface. The summit pieces are represented only by a 

 small oral plate. 



Basals five, small, pentagonal, forming a shallow cup with 

 slightly acute angles. Radials very irregular, two of them 

 consisting of single pieces, the other three of two plates each, 

 connected by suture. The two single plates, which agree in 

 size but not in form with the compound ones, belong to the 

 anterior ray and left postero-lateral one ; they are heptagonal 

 and almost of the same form and size. The three compound 

 ones difl"er from one another ; two of the lower segments are pen- 

 tagonal, that of the right anterior ray hexagonal, its left lateral 

 face being angular. The upper segments are quadrangular, 

 except the one of the right postero-lateral ray, of which the 

 lower corner is slightly truncated. The articular faces form a 

 straight line, and occupy about one-third the width of the radials. 

 They enter deeply the upper surface of the plates, and form at 



