1879.] NATURAL SCIENCES OP PHILADELPHIA. 229 



tome of recent Crinoids, the vault being thus a mere covering or 

 protection. That the mouth was internal in the majority, if not 

 all paleozoic Crinoids, as well as all the Cystideans and Blastoids, 

 is very significant, and impresses us most forcibly with the idea 

 that the earlier Crinoids form a distinct group, and that the solid 

 covering may have been essential under the conditions that pre- 

 vailed in paleozoic times. 



The genus Lichinocrinus, which Hall describes from the Lower 

 Silurian of Cincinnati, affords an instructive example in this 

 respect. In this interesting form, the oral or ventral side was 

 always attached to a shell, coral or other foreign substance ; the 

 dorsal side has a long stem, but whether this was attached to the 

 bottom or not, is not known. The oral side, when found detached, 

 which is of very rare occurrence, shows a large number of striae, 

 which converge to a very small opening in the centre. According 

 to our interpretation, this opening is the mouth, the stria? the food 

 passages, and the shell to which the ventral side is attached, takes 

 the place of the vault, which is as yet undeveloped. 



Another very characteristic distinction between ancient and 

 recent Crinoids is to be found in the comparative^ large size and 

 massive body plates in the fossil, contrasted with the diminutive 

 body and very long and highly developed arms of recent types ; 

 and the same is even more strikingly true as to Blastoids and 

 Cystideans. To illustrate, we might say that in the Pentacrinidse 

 they are fully developed ; that they are in progress of growth in 

 paleozoic Crinoids, and that they are only budding or sprouting 

 in Blastoids and Cystideans ; while in Lichinocrinus, which is 

 probably still lower in the scale of organization, the arms have 

 not yet made their appearance. 



Upon these distinctions, principally, Wachsmuth (Am. Journ. 

 Sci., Sept. 1877, p. 190) proposed to separate the paleozoic from 

 the recent Crinoids, under the name Pal^ocrinoidea, as a sub- 

 order of the Crinoids, of equal rank with the Blastoidea and 

 Cystidea. 



To facilitate a better understanding of the two groups, we now 

 direct attention to certain organs which have been known to exist 

 in Cystideans and Blastoids, and which we think existed in a 

 modified form in the Paleocrinoids. These organs, which were 

 called " hydrospires" by Billings (Am. Journ. Sci., July, 18G9, p. 

 75), occupy rather large spaces within the body in the first-named 



