430 SMITHSONIAN INSTITUTION 



conical extrusion of the perisome back of the posterior oral, curving to the right as we 

 always find it. The number of these plates, about 13, and their relative size, are as actually 

 found in large specimens with the tube intact ; and they are sufficient when erect to support 

 the tube at a height and in a direction to effect the discharge of the excrement entirely 

 away from the mouth. This must be considered in connection with text-figure 8, 1 showing 

 the manner in which the left posterior ray is grooved by pressure against the tube. 



Miller and Gurley's 0. cantonensis is a young specimen of this species from the equiva- 

 lent horizon in Washington County. I have figured their type (PL LXVI, fig. 9), and along 

 with it a mature individual from the same locality and horizon (fig. 10) ; the interbrachials 

 of the latter are not all preserved in place. 



Types. Miller and Gurley's original and -the type of their O. cantonensis are in the 

 University of Chicago ; the others figured and studied are in the author's collection. 



Horizon and locality. Lower Carboniferous, upper part of Keokuk limestone below 

 the Crawf ordsville beds ; Indian Creek, Montgomery County, and Canton, Washington 

 County, Indiana. 



Onychocrinus exsculptus Lyon and Casseday 

 Plates LXIX, figs. 1-9; LXX, figs. 1-7; LXXI , figs. 1, 2 



Onychocrinus exsculptus Lyon and Casseday, Amer. Jour. Sci., (2) XXXIX, i860, p. 78. — Meek and 

 Worthen, Proc. Acad. Nat. Sci. Philadelphia, IX, 1865, p. 140; Geol. Surv. Illinois, II, 1866, p. 247; 

 ibid., V, 1873, p. 498, pi. 14, fig. 4. — Wachsmuth and Springer, Revision Palaeocrinoidea, pt. I, 1879, 

 p. 55. — White, nth Rep. Geol. Surv. Indiana, 1882, p. 365, pi. 40, fig. 1. — Quenstedt, Handbuch 

 Petrefactenkunde, 1885, p. 947, pi. 75, fig. 27. — Springer, Jour. Geology, XIV, 1906, p. 474. 



Forbcsiocrinus ? norwoodi Meek and Worthen, Proc. Acad. Nat. Sci. Philadelphia, i860, p. 389. 



Taxocrinus norwoodi, Meek and Worthen, Proc. Acad. Nat. Sci. Philadelphia, IX, 1865, p. 142. 



Onychocrinus norwoodi, Meek and Worthen, Geol. Surv. Illinois, II, 1866, p. 245, pi. 17, fig. 3, p. 247, 

 text-fig. 26. 



Forbcsiocrinus monroensis Meek and Worthen, Proc. Acad. Nat. Sci. Philadelphia, 1861 (1862), p. 130. 



Onychocrinus monroensis, Meek and Worthen, Geol. Surv. Illinois, II, 1866, p. 244, pi. 17, fig. 7. 



Type of the genus. 



Of the type of O. diversus, but still more elongate, and attaining a larger 



size. Rami longer than the ray below fork, slender, tapering gradually to fine 



terminals ; ramules in numerous clusters, small and delicate. Anal tube strong, 



with socket deeply indented, having a slightly raised margin, and located 



mostly on right side of post. B. Column large, long, tapering gradually from 



its proximal enlargement of uniformly very thin ossicles to alternating 



columnals, with narrow, convex, crenulated rim on the nodals; irregular cirri 



toward the distal end; otherwise generally similar to that of the last two 



species. Average dimensions of 6 mature specimens : Ray to fork, 45 mm. ; 



ramus above fork, 56 mm.; diameter of calyx, 35 mm.; of base, 10.5 mm. 



Maximum specimen; ray 50 mm.; ramus, 75 mm.; total length of crown, 125 



mm.; clusters of ramules, 13 or more. Column of mature specimen, 550 mm. 



(22 inches) long. 



Comparison of the figures, as well as the dimensions above given, with those of the 

 two preceding species, will show at once that this species is far more distinct from them 

 than they are from each other, and that the striking and decisive difference is in the increase 



'P. 51. 



