92 



satisfied myself that in, at least, a large proportion of the paleozoic Cri- 

 noids, the mouth was disconnected altogether from the radial system. A 

 great many species might be referred to in which w^e can see both the 

 centre^ from which the ambulacra proceed, and the mouth ; and at the 

 same time see that they are not in the same place. A long train of 

 reasoning is not necessary — only simple inspection. It will be quite suffi- 

 cient to notice a few of these species to prove that the rule laid down by 

 Prof. Wyville Thompson, is not a general rule. 



Fig. 50. Fig. 51. Fig. 52. 



rig.50. — This figure is a diagram of the interior of the vault of a 

 Crinoid^ which appears to be Batocrinus icosadactylas (Cassiday), a fossil 

 that occurs in the Carboniferous rocks of Kentucky. It was sent to me 

 by Mr. S. S. Lyon, of Jefferson ville, Indiana, several years ago. The 

 test is in a beautiful state of preservation and perfectly empty, so that all 

 of the markings on the inner surface can be distinctly seen. There are 

 twenty-one arms, arranged in five groups (a), and the same number of 

 ambulacral openings {p)^ each just large enough to admit of the entrance 

 of a slender pin. The mouth {mv) is nearly central, and close to it, on 

 the posterior side, there is a small rudely pentagonal space (c) with no 

 markings except several small tubercles The grooves are scarcely at all 

 impressed, and, indeed, I think they never are so in any Crinoid, except 

 in those which have a thick test. In this specimen their course is clearly 

 indicated by the remains of the thin partitions which either separated 

 them or to which the vessels were attached. They do not run directly 

 toward the mouth, as they would do if that organ were the centre of the 

 ambulacral system, but to the small space (c) behind it where there appears 

 to have been situated a vesicle or some other apparatus, to which all of them 

 w^ere united. Whatever may have been the structure of this central 

 organ, from which the five main grooves radiate, it no doubt represented 

 the annular vessel of the recent Echinodermata to which Prof Thompson 

 alludes. 



Fig.51. — represents the structure of an A yiphoracrinus from the Car- 

 boniferous rocks of Ireland, — precise locality and species not determined. 



