FOSSILS OF Tin-: r.iHLixc.Tox duori'. 327 



the vault. That these furrows terminated at the entrance of the ali- 

 mentary canal, under the middle of the vault, as those of Comatula 

 ronvei -e 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 convej'ed to the entrance of the alimen- 

 tary 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 Comatula Jtfediterranea. 



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

 present considerable similarity to that of Crotalocrinus rugosm, except- 

 ing that in that genus, owing to its great number of arms, the ambula- 

 cral 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 TBOOST proposed the name 

 Ctipdla-crlnm we observe a somewhat similar vault, at least in some of 

 the species: also in CoccocrinH*. In such forms there would seem to be, 

 as it were, an intermediate gradation between the modern Criuoids and 

 the prevailing Palaeozoic types, as has been pointed out by Mr. BILLLXGS. 



4. Conciliated support of the digestive sack, in tlie Actinocrinida?. 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 Actinocri- 

 nida\ was noticed by Prof. HALL, in Vol. XLI. p. 261, of the Am. Jour. 

 Sci., in 180G, though he made no suggestions there in regard to the 

 functions it probably performed in the internal economy of these ani- 

 mals. In the second volume of the Illinois Geological Eeports, pub- 

 lished soon after, we figured on page 191. a specimen of Strotocrinus, 

 with this body seen in place, and stated that we regarded it as having 

 been connected with the digestive apparatus of the animal. 



Both in Prof. HALL'S and our own remarks, this organ was spoken 

 of as a convoluted plate. This, however, we now know is not strictly 

 eonect : for. although composed of hard calcareous matter, and in some 

 species somewhat dense in structure, it seems to be always constructed 

 of a great number of minute pieces, and generally has a more or less 

 open or porous texture : while in some cases it presents the appearance 

 of an exceedingly delicate net-work. It seems never to be attached to 

 the bottom of the visceral cavity, though it extends down nearly to the 

 bottom. It is open at both ends (the opening at the lower end being 



