TAXOCRINIDAE 433 



Onychocrinus ramulosus (Lyon and Casseday) 

 Plate LXXII 



Forbesiocrinus ramulosus Lyon and Casseday, Amer. Jour. Sci., XXVIII, 1859, p. 237. — Meek and 



Worthen, Proc. Acad. Nat. Sci. Philadelphia, 1865, p. 140. — Quenstedt, Handbuch Petrefakten- 



kunde, 1885, p. 947, pi. 75, fig. 26. 

 Onychocrinus ramulosus, Wachsmuth and Springer, Revision Palaeocrinoidea, I, 1879, p. 55. — White, 



Geol. Surv. Indiana, nth Rep., 1882, p. 366, pi. 39, figs. 2, 3. — 'Wachsmuth and Springer, N. A. 



Crinoidea Camerata, 1897, p. 75, table B, fig. 7. 



Attaining a large size. Crown elongate, height to width in mature speci- 

 men as 3.7 to 1. Rays strong, short, broadly rounded; free from about IBr 2 . 

 Rami very long, two and one-half times as long as the ray below them; strong, 

 tapering very gradually to fine terminals ending in equal bifurcations. Ramules 

 bilateral, strong, long, given off alternately at intervals of 4 and 3 brachials, 

 branching again several times at long intervals of 3 to 6, and not forming 

 clusters; there are 13 to 15 in mature specimens. Sutures strongly arcuate 

 throughout and patelloid processes often strongly marked. Surface finely 

 granulose, usually found smooth. Average dimension of five large specimens: 

 Ray below fork, 35 mm. ; rami above fork, 87 mm. ; diameter of calyx at IBr 3 , 

 33 mm.; of base, 14 mm.; average of same dimensions in four small ones, 

 11-14-10-6. So the relative elongation of the rami increases greatly with age. 



IBB low, barely visible above the column. BB small in large specimens, 

 but little visible except the post. B. RR and IBr similar in form and size, and, 

 like all brachials throughout the ray, short and from two and one-half to three 

 times as wide as long. IBr 3; IIBr to first ramule, 4, diverging in adjacent 

 rami at a small angle and rarely united for more than one pair above the 

 axillary. Higher orders of Br between ramules varying between 4 and 3; 

 ramules bifurcating on third and fifth brachial, and beyond that up to five 

 times at intervals of 4 to 7 ; they make only a small angle with the main ramus, 

 being joined to it by direct suture or iBr for a distance of several brachials. 

 iBr few, small and irregular, passing quickly into loose perisome, and in 

 mature specimens developed in the higher axils to the seventh or eighth ramule. 

 Anal tube small; socket on right side of post. B which is rather narrow distally. 

 Column strong, with very gradual taper from calyx, passing to slightly alter- 

 nating columnals ; it is very long, enlarges again toward the end, and has a 

 few good-sized cirri in the lower part. Length of column in a moderate-sized 

 specimen, 36 inches — the longest known in the Flexibilia. 



The distinctions between this form and that of the exsculptus group are so obvious 

 that detailed comparison is unnecessary. It would be much more logical to make a new 

 genus for it and the following three species than for the isolated 0. asteriaeforn.is. Lyon 

 and Casseday, having described the species as Forbesiocrinus in 1859, did not include in it 

 Onychocrinus when proposing the genus in i860; and the type specimen, with others accom- 

 panying it in the Lyon collection, still bore the label, Forbesiocrinus, when I acquired it. The 

 species was first referred to this genus by Wachsmuth and Springer in 1879. 



