412 SMITHSONIAN INSTITUTION 



Parichthyocrinus nobilis (Wachsmuth and Springer) 

 Plate LXI, figs. 1-16 



Ichthyocrinus nobilis Wachsmuth and Springer, Proc. Acad. Nat. Sci. Philadelphia, 1878, p. 254 (Separate, 



pi. 2, fig. 7) ; Revision Palaeocrinoidea, pt. 1, 1879, p. 35. 

 Parichthyocrinus nobilis, Springer, Amer. Geologist, XXX, 1902, p. 96; Jour. Geology, XIV, 1906, p. 522, 



pi. 6, fig. 17. 



Type of the genus. 



A large species. Crown low and broad, about as high as wide, rotund, 

 broadly curving from base to infolding arms; widest about the lower IVBr, 

 where height to width is about I to I. Calyx a shallow basin, height to width 

 at IAx, 1 to 4, spreading from base about I to 4. Rays and arms broad and 

 flat, flush with the general curvature, infolding about the fourth bifurcation; 

 sutures arcuate. iBr few, areas narrow and elongate, and but slightly 

 depressed. Surface smooth or finely granular. Dimensions of crown in adult 

 specimen : height, 38 mm. ; width, 3.5 mm. ; base, 6 mm. 



IBB covered by column, but not within the ring of BB. BB low, visible 

 as small triangles beyond the column, except post. B which is very large and 

 wide, encroaching on r. post. R. RR and IBr short and wide, about as 1 to 3, 

 increasing in width upward; r. post. R smaller than those of other rays. 

 IIBr 3 and 4, of about the same size and proportions as IBr, and like them 

 increasing in width upward; IIIBr 4 or 5 on inner ramus and 7 or 8 on outer, 

 increasing slightly in width upward. Thus the whole ray widens reg"ularly 

 up to the lower IVBr, where the greatest expansion of the crown occurs; there 

 is usually one more bifurcation, and all higher brachials are very short and 

 wide. iBr consisting of a few large plates, in adult specimens either 1 large 

 followed by 1 or 2 small ones in the apex, or 2 or 3 large in succession; or in 

 very mature specimens 2 plates in the second range ; in young none at all ; the 

 iBr area does not widen upward, but has about its maximum width in the first 

 range. Anal tube very small and delicate, composed of elongate plates bor- 

 dered by diminutive plates at the right and broken down perisome at the left. 

 Column of moderate size, tapering gradually for a short distance, passing 

 from very thin and equal to alternating columnals, and continuing" smooth and 

 cylindrical. 



This species was founded upon the large specimen shown in figures la, b, described 

 without illustration in the regular edition of the Philadelphia Academy Proceedings, but 

 accompanied by a reduced photograph on a plate circulated with the separate copies of the 

 paper. It was defective in the base and anal side, and from the resemblance of the closely 

 abutting and interlocking arms to those of Ichthyocrinus, the anal side was supposed to be 

 solid. The specimen was unique, and it was not until years afterward that the fine series 

 now in hand were found, illustrating the species and genus in all its phases from the young 

 to very mature. In 1906 I published a figure showing the structure of the anal side as now 

 understood, to further demonstrate the necessity of a new genus for this form (fig. 10b) ; 



