330 PROCEEDINGS OF THE ACADEMY OF 



along the ambulacral canals, perhaps by means of cilia, we are led from analogy 

 to think that the palffiozoic Crinoids subsisted upon similar food, conveyed in 

 the same way lo the entrance of the digestive sack If so, where would there 

 have been any absolute necessity for a mouth or other opening directly through 

 the vault, when, as we know, the ambulacral canals were so highly developed 

 under it from the arm openings to the entrance into the top of the alimentary 

 canal ? Indeed it seems at least probable, that if the soft ventral disc of 

 Comatula had possessed the power of secreting solid vault pieces, as in most 

 types of paheozoic Crinoids, that these vault pieces would not only have covered 

 over the ambulacral furrows, as in the paliBOZoic types, but that they would 

 also have hermetically covered over the mouth, and converted the little flexi- 

 ble anal tube into a solid calcareous pipe, such as that we often call the pro- 

 boscis in the extinct Crinoids. 



From all the facts therefore now known on this point, we are led to make 

 the inquiry whether or not, in all the palaeozoic Crinoids in which there is 

 but a single opening in the vault — whether it is a simple aperture or pro- 

 longed into a proboscis, and placed posterially, subcentrally, or at some point 

 on a line between the middle and the posterior side — this opening was not, 

 iastead of being the mouth, or both mouth and anus as supposed by some, 

 really the anal aperture alone ; and whether in these types the mouth was not 

 geuerally, if not alwa3-s, hermetically closed by immovable vault pieces, so 

 far as regards any direct opening through the vault ? 



We are aware of the fact, that at least one apparently strong objection may 

 be urged against this suggestion, and in favor of the conclusion that the single 

 opening seen in these older Crinoids was the mouth, or at least performed the 

 the double office of both anal and oral aperture. That is, the frequent occur- 

 rence of specimens of these palasozoic species, with the shell oi a, Platyceras in 

 close contact by its aperture, either with the side or the vault of the Crinoid, 

 and not unfrequently actually covering the only opening in the vault of the 

 latter, so as to have led to the opinion that the Crinoid was in the very act of 

 devouring the MoUusk at the moment when it perished. 



Amongst the numerous beautiful specimens of Crinoids found in the Keokuk 

 division of the Lower Carboniferous series at Cravvfordsville, Indiana, there is 

 one species of Platycrinus (P. hemisphsericus), that is so abundant that proba- 

 h\j not less than two hundred, and possibly more, individual specimens of it 

 have been found there by the different collectors who have visited that noted 

 locality ; and, judging from those we have seen, apparently about one-half of 

 these were found with a moderate sized, nearly straight, or very slightly 

 arched and conical Platyceras [P. infundibuluni), attached to one side by its 

 aperture, between the arms of the crinoid, and often so as to cover the single 

 lateral opening in the vault of the same* From the direction of the slight 

 curve of the apex of the Platyceras, it is also evident that it is always placed in 

 such a manner, with relation to the Crinoid, that the anterior side of the Mol- 



floating In the sea-water, came in contact with the ambulacra! furrows of the pinnulte, 

 they were conveyed along these furrows to those of the arms, and thence in the same way 

 into the mouth. He ridicules the idea, sometimes suggested, that the food may have been 

 handed by the pinnuliBor arms directly to the mouth. 



Dujardin and Hup6 also state (Hist Nat. des Zoophytes Echind., p. 18), that the living 

 Comatula was " nourished by microscopic yl///;? and floating corpuscles, which the vibra- 

 tile cilia of the ambulacra brought to the mouth." That they may have sometimes swal- 

 lowed a larger object, that accidentally floated into the mouth, however, is not improbable, 

 and would not, if such was the case, by any means disprove the generally accepted opinion 

 that these animals received their food almost entirely through the agency of their ambu- 

 lacral canals. 



* We at one time thought these shells attached to the side of this Platycrinus to be out 

 of reach of the opening, or supposed mouth, because we had not seen specimens showing 

 the position of the opening in this species, and had supposed, from its similarity to Platy- 

 erinus granulatu!!, Miller, and other species without a lateral opening, that such was also 

 the case with this. We have since seen specimens, however, showing that it has a lateral 

 opening, and therefore belongs to the group Pkurocrinus, so that it is probable these shells 

 often cover this opening. 



[Dec. 



