CLEIOCRINUS. 101 



the law of Wachsmuth and Springer, similar to that of Glyptocrinus fornshetti, 

 — a monocyclic species in which both stem and canal are radial, and which 

 is also from the Lower Silurian, among the earliest Crinoids. 



Granting that there is a dicyclic base, the question remained, what is the 

 exact nature of it ; and what are the five plates lying between the radials '.' 

 Billings, with singular sagacity, called them the "true basals." His state- 

 ment, in the description of C. regius (Dec. IV., p. 53), is as follows : "At 

 first sight there appear to be ten small basal plates, but upon examination 

 five of these are found to be the first plates of the five rays which rest im- 

 mediately upon the upper joint of the column ; the other five are the true 

 basal plates." Wachsmuth and Springer, having classed the genus with the 

 Ichthyocrinidte on account of the strong resemblance of its pliant calyx to 

 that of Icldhi/ocrinus, had supposed that it might possess the basal arrange- 

 ment of the group, viz., 5 basals and 3 infrabasals, both hidden by the 

 column ; and they considered the pentagonal plates between the radials to 

 be interradials. Since it now appeared that the genus is pinnulate, with an 

 arm structure which differentiates it absolutely from all the known Pala?o- 

 zoic Flexibilia, there seemed to me equally good reason to infer the presence 

 of five infrabasals, as in the base of the dicyclic Camerata. 



The superficial aspect of the specimens furnished no information on this 

 point ; and the only important fact gathered from the first examination of 

 them was, as had been pointed out by W. R. Billings in a letter, that the 

 proximal plates of the calyx do not rest immediately upon the upper joint 

 of the column, as stated by E. Billings, but they seem to overlap the 

 column, and form a ring around its upper edge. The two specimens of 

 C. regius both showed this very plainly ; and they also showed the further 

 curious fact that the five radially situate plates of this proximal ring, 

 although having nothing to rest upon or to support them from below, at 

 least exteriorly, are distinctly angular below. 



It was apparent, however, that no further information was to be obtained, 

 unless we could find some means of seeing what is underneath the column. 

 My examination of the specimens gave no hope of being able to detach 

 the column in either of them ; but after a very careful study of specimen B, 

 under a strong magnifier, I came to the conclusion that it might be possible 

 to get at the inside of the base by removing a part of the plates above it. 

 This specimen preserved the first two rings of plates nearly in situ ; it was 

 slightly flattened by pressure, and on the side opposite that shown in Bil- 



