TROOST 's CRINOIDS OF TENNESSEE E. WOOD. 39 



It occurs in the Carboniferous limestone in the vicinity of Huntsville and in the 

 oolitic limestone of the Cumberland Mountains, Tennessee — in the latter locality I 

 found only fragments. 



The following is the description of Platycrinus polydactylus by 

 Troost: 



It is distinguished from P. huntsvillx in the division of the hands [arms] — in this 

 species one of the hands [arms] is subdivided into two as in the P. huntsvillx, while 

 the other is subdivided into three so that we have alternately 2 and 3 or 25 fingers 

 [ramuli] in all while in the P. huntsvillx we have only 20 — besides the body is more 

 elongated. 



Observations. — The first published description of this species is by 

 Wachsmuth and Springer [1897], although the name was proposed by 

 Troost in 1850. Troost separated Platycrinus polydactylus from 

 P. liuntsvillse on account of the more freely branching arms of the 

 former, but Wachsmuth and Springer state that in a large number of 

 individuals the branching of the arms is too variable to be used for 

 the separation of species. 



Formation and locality. — St. Louis group. Huntsville, Alabama; 

 Hardin County, Illinois. 



Cat. Nos. 39886, 39887, U.S.N.M. 



PLATYCRINUS SAFFORDI Hall. 



Plate 15, fig. 10. 



Platycrinus saffordi Troost, MSS., 1850. — Hall, Geol. Rep. Iowa, I, Pt. 2, 1858, 

 p. 634, pi. xvin, figs. 5, 6. — Shumard, Trans. Acad. Sci. St. Louis, II, No. 

 2, 1866, p. 389 (catalogue name). — Wachsmuth and Springer, Rev. Palaeo- 

 crinoidea, II, 1881, p. 74 (catalogue name). — Miller, North Amer. Geol. and 

 Pal., 1899, p. 271 (catalogue name). — Keyes, Missouri Geol. Surv., IV, 1894, 

 p. 212, pi. xxv, fig. 1. — Wachsmuth and Springer, North Amer. Crinoidea 

 Camerata, 1897, p. 694, pi. lxvii, figs. 1-3.— Weller, Bull. No. 153, U. S. 

 Geol. Surv., 1898, p. 445 (catalogue name). 



Troost says of this species: 



This large crinoid has excited in me no less admiration than I experienced when I 

 examined for the first time the splendid Actinocrinites humboldti [Actinocrinus mag- 

 nificus Wachsmuth and Springer.] It is equally large and beautifully ornamented, 

 but equally delicate and fragile. Only mutilated specimens are now discovered of it. 

 One of these, nevertheless, in my collection shows enough of its generic characters to 

 rank it amongst the genus Platycrinites. I possess of it a complete pelvis [base] and 

 another which contains yet two perfect plates of the scapulars [radials]. 



The pelvis [base] has the form of a large basin considerably extending beyond the 

 lower part of it [i.e. the surface for attachment of the column] the superior rim being cut 

 out with five concave spaces, into which are placed five somewhat irregular, quadri- 

 lateral scapulars [radials]. These scapulars [radials] have no [an] excavation in the 

 center of the superior margin as is the case in the scapulars [radials] of the Platycrinites, 

 but have a horseshoe-like, small plate (arm plate) which inclines backwards forming 

 almost a right angle with the surface of the plates, and is externally ornamented with 

 some projecting tubercles to which [i. e. to this plate] seems to have attached the arms. 



On none of the two pelves [bases] that I possess are any traces of junction of the 

 plates visible, which junctions, even if they existed, would have been obliterated by 



