1869.] MEEIC AND WORTHEN — ON PALiEOZOlC CRINOIDEA. 445 



advance of the opening. That the ambulacral canals here, under 

 this point of convergence of the furrows in the under side of the 

 vault, always came together and connected with the upper end of 

 the convoluted frame-work of the digestive sack, we can scarcely 

 entertain a doubt. 



Now in looking at one of these specimens, especially an internal 

 cast of the vault, showing the furrows (or casts of them) starting 

 from a central, or nearly central point, and radiating and 

 bifurcating so as to send a branch to each arm-base, while the 

 opening or proboscis of the vault (or the protuberance represent- 

 ing it in the cast) is seen to occupy a position somewhere on a 

 line between this central point from which the furrows radiate, 

 and the posterior side, one can scarcely avoid being struck with 

 the fact, that this point of convergence of the ambulacra, under 

 the vault, bears the same relations in position to the opening of 

 the vault, that the mouth of a Comatula does to its anal opening. 

 And when we remember that eminent authorities, who have 

 dissected specimens of the existing genus Comatula, maintain 

 that these animals subsisted on microscopic organisms floating in 

 the sea-water, such as the Diatomacce, minute Eiitomostracu, 

 etc.,* which were conveyed to the mouth along the ambulacral 

 canals, perhaps by means of cilia, we are led from analogy to 

 think that the Palaeozoic Crinoids subsisted upon similar food, 

 conveyed in the same way to 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 



* Brouu mentions the fact (Klassen des Thierreichs. Actiuozua, II> 

 p. 211), th^it the remains of Biatomacece, of the genera Navlcula, 

 Jctmocyclus, CoscinocUsous, and of Eutomt>straca, were found in the 

 stomach of Comatula, and suggests that, when such objects, in floating 

 in the sea-water, came in contact with the ambulacral farrows of the 

 piuure, 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 

 pinnulse or arms directly to the mouth. 



Dujardin and Hupe also state (Hist. Xat. des Zoophytes Behind., p. 

 18), that the living Comatula was " nourished b}' microscopic Alc/o} and 

 floating corpuscles, which the vibratile cilia of the ambulacra brought 

 to the uiouth." That they may have sometimes swallowed a larger 

 object, that accidentally floated into the mouth, however, is not impro 

 bable, 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 ambulacral canals. 



