60 BULLETIN 64, UNITED STATES NATIONAL MUSEUM. 



Formation and locality. — Keokuk horizon of the Tullahoma forma- 

 tion. White's Creek Springs, Tennessee. 

 Cat. No. 39973, U.S.N.M. 



AGARICOCRINUS CRASSUS Wetherby. 



Plate 14, figs. 5, 6. 



Agaricocrinus tuberosus Troost (in part), Proc. Amer. Ass. Adv. Sei., II (read 

 1849), 1850, p. 60 (nomen nudum); MSS., 1850. 



Agaricocrinus crassus Wetherby, Joum. Cincinnati Soc. Nat. Hist., IV, 1881, 

 p. 178, pi. v, fig. la, b. — Wachsmuth and Springer, Rev. Palseocrinoidea, 

 III, 1885, p. 105.— Miller, North Amer. Geol. and Pal., 1889, p. 220.— 

 Wachsmuth and Springer, North Amer. Crinoidea Camerata, 1897, p. 499, 

 pi. xxxix, figs. 2a, 6; pi. xl, fig. 4. — Weller, Bull. No. 153, U. S. Geol. 

 Surv., 1898, p. 69 (catalogue name). 



Observations. — One of Troost's specimens of Agaricocrinus agrees 

 with A. crassus Wetherby in the number and arrangement of the 

 plates, the number of arms, the flattened base, and the wide anal 

 area with projecting arms. The chief difference from Wetherby's 

 type is in the greater convexity of the plates of the latter, but Troost's 

 specimen is silicified and the outer layer entirely removed, so that the 

 plates may have been more convex than now appears. 



The present specimen shows long first brachials which reach to the 

 top of the arm bases, differing in that respect from the figure of the 

 species given by W T achsmuth and Springer [1897, plate 39, fig. 2b]. 

 The original description is meager, relating mainly to the general form 

 and the plates of the tegmen, but the type figure shows a specimen 

 with first interbrachiais bending over the margin of the calyx, and 

 the second interbrachiais are not visible in a side view. 



Formation and locality. — Keokuk horizon of the Tullahoma forma- 

 tion. White's Creek Springs, Tennessee. 



Cat. No. 39974, U.S.N.M. 



AGARICOCRINUS PONDEROSUS, new species. 



Plate 14, figs. 1, 2. 



Agaricocrinus tuberosus Troost (in part), Proc. Amer. Ass. Adv. Sci., II (read 

 1849), 1850, p. 60 (nomen nudum). 



This fme species has a deep basal excavation and a tegmen of mod- 

 erate height leaving a restricted space for the animal. 



The basals and radials at the bottom of the basal excavation are 

 concealed by the matrix. First primibrachs rectangular and nearly 

 twice as wide as long. Primaxils large, irregular in shape, followed 

 by one secundibrach on each side in the posterior rays and on the 

 posterior side of the antero-lateral rays. The secundibrachs are fol- 

 lowed by two series of tertibrachs, from each of which an arm arises. 

 On the anterior side of the antero-lateral rays and in the anterior ray 



