Talbot — New York Helderbergian Crinoids. 31 



A single individual of this species was found by Professor 

 S clinch ert and was presented by him to the Yale University 

 Museum. It differs from other species of the genus, principally 

 in the shape of the crown, the straight sides of the cup being 

 very characteristic. It resembles I. Icevis more closely than any 

 other, but differs from that species in the divisions of the rays 

 and in the fact that the suture lines are not wavy. 



Horizon and locality. — Lower third of the New Scotland 

 limestone near Clarksville. 



Holotype in the Yale University Museum. 



Too little is known of the following Helderbergian crinoids 

 to make definite statements in regard to their classification : — 



Genus, Aspidocrinus Hall. 



Aspidocrinus callosus Hall. 



Aspidocrinus callosus Hall, Nat. Hist. N. Y., Pal., vol. iii, 1859, p. 123, pi. 

 5. figs. 13 and 14. — Wachsmuth and Springer, Rev.. Palaeocr., Pt. II, 1881, 

 p. 228 ; Proc. Phila. Acad. Nat. Sci., vol. xxxiii, 1882, p. 402. 



Aspidocri?ius digitatus Hall. 



Aspidocrinus digitatus Hall, Nat. Hist. N. Y.,Pal., vol iii. 1859, p. 123, pi. 

 5, figs 19 and 20. — Wachsmuth and Springer, Rev. Palaeocr., Pt. II, 1881, p. 

 228 ; Proc. Phila. Acad. Nat. Sci., vol. xxxiii, 1882, p. 402. 



Aspidocrinus scutelliformis Hall. 



Aspidocrinus scutelliformis Hall, Nat. Hist. N. Y., Pal., vol. iii, 1859, p. 

 122, pi. 5, figs. 15-18. — Wachsmuth and Springer, Rev. Palaeocr., Pt. II, 

 1881, p. 228 ; Proc. Phila. Acad. Nat. Sci., vol. xxxiii, 1882, p. 402. 



These species of Aspidocrinus present difficulties that are 

 as yet unsolved. Hall described the forms as bases of crinoid 

 cups, but Wachsmuth and Springer listed them doubtfully as 

 crinoid roots. There are two reasons, at least, for thinking 

 that they cannot be crinoid roots or basal expansions of col- 

 umns. If they are basal expansions, the concave side must 

 be the under side and this must have rested on the mud 

 of the sea floor. One specimen of A. scutelliformis in the 

 Yale University Museum has a bryozoan attached to this con- 

 cave surface, proving that this surface could not have rested on 

 the mud. If, on the other hand, these specimens represent the 

 base of a cup, the presence of the bryozoan might be explained 

 by supposing that its growth took place after the upper part 

 of the dead calyx had been broken off but while the lower 

 part still remained attached to the column. 



Again, in undisputed examples of basal expansions, the lower 

 or distal joints of the column enlarge and the segmentation of 

 the column is continued into the upper part of the enlarged 

 base. No such segments are visible in any of the specimens 

 in question. In every good specimen, there is a clear-cut cir- 



