456 Mr. C. Wachsmuth on the Internal and 
Scaphiocrinus, and all genera with an inflated or balloon- 
shaped ventral sac. Among the latter the centre of radiation 
is frequently found to be pushed toward the anterior side, so 
that, owing to the great size of the sac at its junction with the 
dorsal cup, it does not occupy the centre of figure. 
Among all groups of Crinoids, the Cyathocrinide undergo 
the least amount of change in the course of time. They are 
represented in the Lower Silurian by several genera; and Cya- 
thocrinus is the only genus recognized in the Permian. In all 
intermediate formations we find Crinoids with five basals, five 
subradials, and five radials; and it is worthy of note that the 
Cyathocrinide, in the structure of their vault, bear closer re- 
semblance to the recent Crinoids than almost any other group, 
and seem to hold an intermediate position between modern 
and Paleozoic types. Ifthe alternating plates covering the 
furrows could be turned back at the vault by the animal as 
the Saumplatten of the arms, then the food-groove of these 
Crinoids was open throughout, as in recent forms. This might 
possibly have been the case in Cyathocrinus towensis ; but I 
even doubt it here, as the corresponding plates in other closely 
related species, though arranged upon the same fundamental 
plan, present rather an aspect of true vault pieces. The Cu- 
pressocrinida and Cyathocrinide thus fall naturally into a 
group by themselves, having the vault supported by con- 
solidating plates, and covered by an immovable arch of small 
plates. 
The next group, including TYaxocrinus, Forbesiocrinus, 
Onychocrinus, Ichthyocrinus, Lecanocrinus, and probably other 
genera, is one in which, of all Paleozoic Crinoids, the vault is 
least known. The Taxocrinide (for such I will call them) 
have hitherto been described as being covered with some soft 
material instead of solid plates, even by Dr. Schultze, though 
he describes and figures a Yaxocrinus with a long, heavy, 
plated proboscis, which could not have been supported upon a 
soft skin*. In this group the plates of the radial series are 
indented on their upper margins more or less deeply for-the 
reception of a protuberance from the lower side of the succeed- 
ing plate. The indentation of the upper margin does not 
extend throughout the thickness of the plate ; and in Forbesio- 
erinus it is filled by a superficial patelloid plate, which is 
* I believe Dr. Schultze is mistaken in referring his 7. briareus to 
Taxocrinus, as it lacks all the characteristic features of the genus. Its 
rather large subradials, the large first radials as compared with the suc- 
ceeding radials, the single anal plate upon which the heavy proboscis 
rests, indicate that it belongs to Cyathocrinus or some allied genus. His 
T. gracilis may prove to be Graphiocrinus or Scaphiocrinus(?). 
