Glyptocrinus Redefined and Restricted, ete. 221 
The vault has never been hitherto clearly defined, and some authors 
have entertained very erroneous opinions respecting it. I am glad, 
therefore, to be able, through the assistance of specimens from the 
magnificent collection of Dr. R. M. Byrnes, to more particularly and 
more fully describe it. 
It is somewhat convex in the central part, and undulates toward 
each intertertiary area. It is composed of numerous polygonal plates. 
Those in the central part are the larger ones, and each of these bears a 
central tubercle, which is sometimes prolonged so as to be designated 
a spine. Toward the margin, or rather following the undulations 
toward the intertertiary areas, the plates are smaller and possessed of 
slight convexity. They unite in the depressions in the intertertiary 
areas with the plates of the calyx, or rather the interprimary radials 
graduate through the intersecondaries and intertertiaries to the plates 
of the vault without any lineof separation. The plates become smaller 
as they approach the inner face of the arms, over the swelling undula- 
tions of the vault, and continuing to decrease in size, form a somewhat 
granular, continuous integument, that covers the ambulacral furrows. 
This continuation of the vault up the inner side of the arms has been 
observed for the distance of an inch above the vault, and no doubt ex- 
tended as far as the arm furrow itself. The pinnules do not cover 
the ambulacral grooves. Notwithstanding the magnificent pinnules 
upon the sides of the arms, in this genus, the ambulacral furrows are 
covered with small plates between the rows of pinnules, and the pin- 
nules have nothing to do with covering the furrows. 
« The reason emphasis is placed upon the fact is, Wachsiauth and 
Springer have doubted and even denied it. They say in their “ Revi- 
sion of the Palseocrinoidea,” p, 25 : 
“Tt is important to note, that in those genera in which the ambu- 
lacral groove is thus covered, no regular pinnules have ever been 
observed, and, moreover, the construction is such that no additional 
pinnulee could have existed ; while on the other hand no covering has 
ever been discovered in forms with true pinnule.”’ 
And, finally, they come to the conclusion that the plates covering 
the ambulacral groove were homologous with the pinnule, or, as they 
say, ‘in fact rudimentary pinnule.”’ 
It is not easy to understand how pinnules should, in any case, act 
as a covering to an ambulacral groove, and as I have never seen a 
specimen which was calculated to make any ‘such impression on my 
mind, I am unable to realize how those authors arrived at such a con 
