Summit Structure of Pentremiles. 499 



CdlLlOCRIXrS (n. g.) 

 Etym. KOikia, venter; Kpivov, liliuni. 

 Generic formula and description. 



Basal pieces, 5. 



Subradial pieces, 5. 



Radial pieces, 5x2, subequal in size. 



Anal pieces, 4 or 5 visible when the arms are in place. 



Arms 10, bifurcating once or more, and composed of 

 single series of pieces, with obliquely alternating, or 

 parallel sutures. 



It will be seen that the above formula contains nothing 

 that the formula of Poteriocrmus would not include, but 

 that it is more restricted. Compared with Scaphiocriuus, 

 with which it is associated, the entire specimens are propor- 

 tionally much shorter, more robust, the ventral sack much 

 larger and more expanded than the inflated probosces of 

 some species of Scaphiocrinus, which occupy a similar 

 position. The species now known have not the bent or 

 corrugated body-plates, nor the constricted arm-plates so 

 common in that genus. The prominent features of this 

 genus are. First, The large inflated ventral sack, varying 

 in size in different species, from four or five times the ca- 

 pacity of the calyx, to ten or twenty times that capacity. 

 It is widest at the top, in some cases extending above the 

 tips of the arms, — the lower part being contracted be- 

 tween the arms like the neck of a balloon, — and joins by 

 this to the anal series. 



Second, The proportionally small calyx formed by the 

 basal, subradial, radial and first anal plates, which is so 

 small as to render it certain that it could not contain the 

 necessary internal organs for the support of the other parts. 

 These organs must have been located in the plated sack, 

 which I have denominated the ventral sack; thus reversinir 



