438 THE CANADIAN NATURALIST. [BeC. 



form, of the movable pieces composing what is often called the 

 ovarian pyramid in the Cystids, but certainly have all the 

 appearances of true fixed vault-pieces, and scarcely project above 

 the others surrounding them. Consequently we cannot believe 

 it at all probable that this genus had a central mouth, opening 

 directly through the vault ; though its ambulacral canals evidently 

 converged from the arm-bases to the middle of the vault, partly 

 above the outer vault-pieces, and under those composing the 

 middle of the vault. That these furrows terminated at the entrance 

 of the alimentary canal, under the middle of the vault, as those 

 of G matula converge to the mouth, in the same central position, 

 is highly probable ; and, as will be seen further on, we are much 

 inclined to believe that the minute organisms upon which we are 

 led, from analogy, to think these animals subsisted, were conveyed 

 to the entrance of the alimentary canal along the ambulacral 

 furrows, without the agency of any proper mouth, opening directly 

 through the vault. Hence we think it probable that the small 

 tube, usually called the proboscis, situated near the posterior side 

 of the ventral disc, rather corresponds to the tubular anal opening 

 similarly situated in Comatida Mediterranea. 



From our description of the vault of these species, it will be 

 seen to present considerable similarity to that of Crotalocrinus 

 rugosus, excepting that in that genus, owing to its great number 

 of arms, the ambulacral furrows, or canals, bifurcate several 

 times between the middle of the vault and the arm-bases, while in 

 Crotalocrinus there is no lateral proboscis, nor, apparently, even 

 any visible opening, judging by the figures we have seen, though 

 we suspect it may have a small opening at the periphery of the 

 ventral disc, on the posterior or anal side. In the group of 

 depressed Platycrini for which Troost proposed the name 

 Cupelloecrinus we observe a somewhat similar vault, at least in 

 some of the species ; also in Coccocrirms. In such forms there 

 would seem to be, as it were, an intermediate gradation between 

 the modern Crinoids and the prevailing Palreozoic types, as has 

 been pointed out by Mr. Billings. 



4. Convoluted support of the digestive sack, in the Actinocri- 

 nidcB. The presence of a large convoluted body, resembling in 

 form the shell of a Bulla or Scaphander, within the body of 

 several types of the Actinocrinidce, was noticed by Prof Hall 

 in vol. xii, p. 261 of the Am. Journ. Sci., in 1866, though he 

 made no suggestions there in regard to the functions it probably 



