TROOST ? S CRINOIDS OF TENNESSEE E. WOOD. 65 



and is followed by three plates above which there are apparently two 

 plates, but this can not be determined with certainty. 



The exact arrangement of the tegmen plates can not be made out, 

 as they have been unequally separated by deposition of silica. Each 

 plate bears at its center a sharp spine-like node. Proboscis unknown. 



Observations. — This species resembles Batocrinus Jionorabilis Miller 

 and Gurley in general form and surface ornament, but it differs in 

 having but one instead of four interbrachial plates and in the presence 

 of eighteen instead of twenty arms. It also resembles B. grandis, 

 but differs from that species, as well, in the single interbrachial plate 

 and fewer arms. 



The resemblance to Eretmocrinus praegravis Miller is confined 

 mainly to the nodes of the surface, which are, however, less prominent 

 in the present species. The latter differs further from E. praegravis 

 in having the dorsal cup much higher than the tegmen and in the 

 greater number of arms. 



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

 tion. White's Creek Springs, Davidson County, Tennessee. 



Cat. No. 39892, U.S.N.M. 



BATOCRINUS SAYI (Troost). 



Plate 13, figs. 7, 8. 

 Actinocrinites sayi Troost, MSS., 1850. 

 The original description by Troost is as follows : 



I am not certain whether this crinoid belongs to the Actinocrinites. The plates 

 forming the cup of figs. [7 and 8] exhibit certainly the arrangement of this genus but 

 it is widely different in regard to its capital integument; but as naturalists class these 

 fossils according to the arrangement of the plates that compose these bodies, I place it 

 together with Actinocrinites fibula [Dizygocrinus saccutus, pi. 5, figs. 1-6] which is 

 equally doubtful, being placed provisionally in this genus. 



It is basin shaped, composed of tumid plates. The arms which do not project 

 beyond the rim, which is circular, are ten [?] in number. The capital integument is 

 level, and does not terminate in a proboscis [?]. The centre is taken up by an irregular 

 circular plate, the top stem joint which seems to have a circular aperture in its centre. 

 The remains of the integument are covered with irregular polygonal plates each of 

 which is elevated in its centre. 



Supplementary description. — The single specimen representing 

 this species is wholly silicified and much distorted by compression, 

 but the lower plates of the calyx are well preserved. 



Basals comparatively small, the upper half of each plate rising at 

 right angles to the lower half and having its lateral angles trun- 

 cated. The three basals together form a short hexagonal prism 

 from which the radials diverge abruptly. 



Radials very large. Greatest width of a single radial equal to 

 the entire width of the basal prism. First primibrachs but slightly 

 wider than long. Primaxils of about the same size as the first 

 primibrachs, wider than long. First secundibrachs as large as the 

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