NATURAL SCIENCES OF PHILADELPHIA. 329 



that brought them to light in this instance may not again occur for centuries 

 to come, with regard to another specimen. That they correspond to the am- 

 bulacra! canals seen extending from the arm-base to the mouth, on the outside 

 of the ventral disc in Comatida, is clearly evident. 



The presence of furrows radiating from the central region of the under side 

 of the vault to the arm-openings, in various types of palaeozoic Crinoids, must 

 have been frequently observed by all who have had an opportunity to examine 

 the inner surface of this part. Messrs. deKoninck and Lehon figure a portion 

 of the vault of Actmocnnus slellaris, in their vulnahle Recherches sur les Crinoides 

 du Terr. Curb, de la Belgiqiie, pi. iii, fig. 4 f., showing these furrows, which they 

 seem to have regarded as the impressions left by the muscles of the viscera. 

 The inner surface of the vault of most of our western Carboniferous Cri- 

 noids is known to have these furrows more or less defined, either from 

 specimens showing this inner surface, or from natural casts of the same. In 

 some instances they are very strongly defined from the central region outward 

 to the arm-bases, to each of which they send a branch. In Actinocrinus orna- 

 tus, Hall, for instance, they are generally so strongly defined as to raise the 

 thin vault into strong radiating ridges, separated by deep furrows on the outer 

 side. In Strotocrinus, the vault of which is greatly expanded laterally, and 

 often flat on top, these internal furrows, in radiating outward, soon become 

 separated by partitions, and as they go on bifurcating, to send a branch to 

 each arm, they actually assume the character of rounded tubular canals, some 

 distance before they reach the arm-bases. 



That these furrows or passages of the inner side of the vault were actually 

 occupied during the life of the animal by the ambulacral canals as they radi- 

 ate from the top of the convoluted digestive sack to the arm-openings, we think 

 uo one will for a moment question, after examining Mr. Wachsmuth's speci- 

 men of Actinocrinus proboscidialix, which we have described, showing all these 

 parts in place. It is also worthy of note, that in all the specimens of various 

 types in which these furrows of the under side of the vault are well known, 

 whether from detached vaults, or from casts of the interior of the same, they 

 never converge directly to the opening of the vault, but to a point on the anterior side 

 of it, whether there is a simple opening or a produced proboscis. The point to 

 which they converge, even in types with a decidedly lateral opening of the 

 vault, is always central or very nearly so, and even when the opening is nearly 

 or quite central, the furrows seem to go, as it were, out of their way to avoid 

 it, those coming from the posterior rays passing around on each side of it to 

 the point of convergence of the others, a little in 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 protuber- 

 ance representing 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 poste- 

 rior 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 Comatida 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 Diatomacece, minute Entomostraca, etc.,* which were conveyed to the mouth 



* Bronn mentions the fact (Klassen des Thierreichs. Aetinozoa, II, p. 211), that the re- 

 mains of Diatomacese, of the genera Navicula, Actinocydus Coscinodiscus, and of minute Kntom- 

 ostraca were found in the stomach of Comatula, and suggests that, when such objects, in 



1868.] 22 



