42 BULLETIN 64, UNITED STATES NATIONAL MUSEUM. 



Observations. — Doctor Troost's specimen of this species is missing, 

 but his figure is sufficiently good to show that it should be referred 

 to Talarocrinus symmetricus Lyon and Casseday. 



Formation and locality. — Bangor limestone. Near Craborchard, 

 Cumberland Mountains, Tennessee. Doctor Troost reports frag- 

 ments of the species from the Silurian of Decatur County, but these 

 are probably incorrectly identified. Also from the upper part of the 

 St. Louis limestone. Grayson, Edmondson, and Pulaski counties, 

 Kentucky. 



TALAROCRINUS SIMPLEX (Shumard). 



Plate 13, fig. 1. 

 Doliolocrinites ovalis Troost, MSS., 1850. 



Dichocrinus simplex Shumard, Trans. Acad. Sci. St. Louis, I, 1857, p. 74, pi. I, 

 figs. 2a, b. — Hall, Rep. Geol. Surv. Iowa, I, Pt. 2, 1858, p. 654, pi. xxn, 

 figs. 12a, 6; Suppl. Rep. Geol. Surv. Iowa, 1860, pi. i, figs. 4a-c. — Shumard, 

 Trans. Acad. Sci. St. Louis, II, No. 2, 1866, p. 366 (catalogue name). — Wachs- 

 muth and Springer, Rev. Palaeocrinoidea, II, 1881, p 84 (catalogue name). 



Talarocrinus simplex Keyes, Missouri Geol. Surv., IV, 1894, p. 205, pi. xxv, fig. 

 6. — Wachsmuth and Springer, North Amer. Crinoidea Camerata, 1897, p. 

 790, pi. lxxviii, figs. 8a, 6.— Weller, Bull. No. 153, U. S. Geol. Surv., 1898, 

 p. 624 (catalogue name). 



The original description by Troost is as follows : 



This crinoid is one of the most simple that I have met with. It is formed of twelve 

 more or less elongated, pentagonal or arrow-head shaped plates — six [two] of which 

 (the short ones) forming the pelvis [base] having the point downwards; this point is 

 truncated having a circular cavity in which is fixed a cylindrical column; the superior 

 margins on both sides bevelled and receive between them six larger scapular plates, 

 [five radials and the anal plate] filling the reentering angles of the pelvic [basal] plates. 

 These six scapular plates are more deeply truncated at the acute angle forming, when 

 joined together, the rim of the visceral cavity which has interiorly six semilunar exca- 

 vations for six [five] arms. 



Observations. — Doctor Troost's specimen of Doliolocrinites ovalis is 

 apparently a Talarocrinus simplex (Shumard). Safford [1869, p. 346] 

 and Hall [1858, p. 655], both of whom probably saw the original 

 specimen, have referred it to this species. The statement that there 

 are six basals is undoubtedly an error. Observing suture lines below 

 two of the radials, Doctor Troost has assumed that they occurred 

 symmetrically all around the base. This assumption of a completely 

 radial symmetry is common in the earlier descriptions of crinoids. 



Formation and locality. — Tullahoma formation. Near Gallatin, 

 Tennessee. Also recorded from Spergen Hill, Indiana, St. Genevieve 

 County, Missouri, and from Kentucky. 



Cat. No. 39984, U.S.N.M. 



