184 CO. Wachsmuth—Structure of Paleozoic Crinoids. 
the base of a proboscis, and the consolidating plates are partly 
covered, leaving but a small uncovered space in the form of a 
delta in the interradial areas. The central opening is vaulted 
over by a number of various sized pieces, the largest one occu- 
pying the side toward the proboscis. The shallow groove be- 
tween the sutures of the consolidating plates is arched by a 
double series of alternating plates, forming underneath a pas- 
ge for the ambulacral canal and food groove. The vault, thus 
closely resembling that of Synbathocrinus, was in all probability 
arranged on a similar principle in Cupressocrinus. The same 
plan, with slight modifications, prevailed in Poteriocrinus, 
Scaphiocrinus and all genera with an inflated or balloon-shaped 
ventral sac. Among the latter, the center of radiation is fre- 
quently 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, 1t does not occupy the center of figure. 
mong all groups of Crinoids, the Cyathocrinide undergo 
the least amount of change in the course of time. They are 
noids was open throughout, as in recent forms. This might 
ibly have been the case in Cyathocrinus Jowensis, but I 
even doubt it here, as the corresponding plates in other closely 
related species, though arranged upon the same fen 
We by themselves, having the vault supported by consoli- 
_<— plates, and covered by an immovable arch of small 
plates. 
The next group is one in which of all Paleozoic Crinoids the 
vault is least known, including Taxocrinus, Forbesiocrinus, Ony- 
chocrinus, Ichthyocrinus, Lecanocrinus, and probably other gen- 
era. The Taxocrinide, for such I will call them, have hitherto 
been described as being covered with some soft material inste 
of solid plates, even by Dr. Schultze, though he describes and 
figures a Taxocrinus with a long heavy plated proboscis, whic! 
could not have been supported upon a soft skin. * In this 
* I believe Dr. Schultze is mistaken in referring his Z briareus to Taxocrinus 
as it lacks all the istic features of the genus. Its rather large subra- 
