680 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
species, and different from P. Huntsville ; but upon examining the arm 
structure, basals and stem, it will be found that they differ only slightly in 
the form of the calyx and the matter of ornamentation, one being cup-shaped 
and ornamented, the other globular and smooth. On comparing them with 
the specimens from Huntsville, it will be seen that similar variations occur 
among them also, along with all sorts of transition forms. The two forms 
were evidently regarded by Meek and Worthen as specifically distinct from 
P. Huntsville, for the Worthen collection contains a large number of fine 
specimens from Alabama, labeled P. Huntsville. 
In 1861, S. A. Miller described under P. alabamensis a small, crushed 
specimen from Huntsville, but neither figure nor description gives a correct 
idea of the species, and he did not state in which division of the “ Subcar- 
boniferous rocks” it was found. He did not define the peculiarities of the 
arm structure, which are so characteristic of P. Huntsville, and indeed the 
description would apply equally well to other forms. It is very curious that 
Meek and Worthen described the arm structure, but did not represent it in 
their figure ; while on the other hand Miller indicated it in his figure with- 
out mentioning it in the description. Priority would give the first of Meek 
and Worthen’s names to the species, if any of the above descriptions are to 
apply; but this would lead to confusion, and would establish an aberrant 
form for the typical one. Under all the circumstances, we have thought 
best to redescribe the species under Troost’s name, thus giving the credit 
to the pioneer naturalist who discovered, recognized, and called attention 
to the new form. | 
For the last ten years one of us has spent a month or two every year at 
Huntsville, and obtained of this species over a thousand specimens, in all 
kinds of preservation, and of all sizes, from 9 mm., including arms, to 
50 mm., and intermediate stages, which give most valuable information 
upon the variability of this species and the Crinoids generally, and also 
upon the changes due to growth. If we were following the practice ot 
some paleontologists, we would be able by picking out individual speci- 
mens to make out of this one species half a dozen or more. In some speci- 
mens the plates appear altogether smooth, without showing in other parts 
any evidence of erosion or weathering; while others have well marked nodes, 
separate or confluent. In still others the proportion of. height to width of 
the calyx varies considerably. All these specimens, however, are character- 
ized by certain peculiarities by which they can be identified at once as be- 
