680 THE CEINOrDEA CAMERATA OF XORTH AMERICA. 



species, and different from P. Huntsvillce ; 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. Huntsvillce, for the Worthen collection contains a large number of fine 

 specimens from Alabama, labeled P. Huntsvillce. 



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. Huntsvillce, 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 considerablj'. All these specimens, however, are character- 

 ized by certain peculiarities by which they can be identified at once as be- 



