1881.] NATURAL SCIENCES OP PHILADELPHIA. 261 



secondary radials forming part of the calj^x, and in having the 

 anal opening through the vault, and not at the end of a tube. It 

 differs from Pterotocrinus in the very different form of the calyx ; 

 in having no teiliary radials in the calyx ; in the form of the 

 dome, and the absence of lobed processes. 



Geological Position^ etc. — The genus is known onlj^ from the 

 St. Louis and Kaskaskia groups of the United States. 



We recognize the following species : — 



*t857. Talarocrinus cornigerus .^humard. (Dichocr. cornigerus.1 Type of the 

 genus. Trans. Acad. Sci. St. Louis, i, p. 72, PI. 1, figs. 1 a, b ; Pterotocr. 

 cornigerus Shumard, 1866, Cat. Pal. Foss. N. Amer., i, p. 393 ; S. A. Miller, 

 Pterotocr. cornigerus, Catal. Pal. Foss., p. 89. Kaskaskia limest. Frank- 

 lin Co., Ala. 



*1860. Talarocr. elegans Cass, and Ljon. (Dichocr. elegans.) Proc. Am. Acad. 

 Arts and Sci., v, p. 22. St. Louis limest. Edmonson Co., Ky. 



*1857. Talarocr. sexlobatus Shumard. (Dichocr. sexlobatus). Trans. Acad. Sci. 

 St. Louis, vol. i, p. 6, PI. i, figs. 3 a, b, c ; S. A. Miller (Pterotocr sexloba- 

 tus), Catal. Pal. Foss., p. 89. Kaskaskia limest. Russelville, Ky. 



*1860. Talarocr. symmetricus Cass, and Lyon. (Dichocr. symmetricus.) Proc. 

 Am. Acad. Arts and Sci., vol. v, p. 22. Ka.^kaskia limest. Edmonson 

 Co., Ky. 



10. PTEEOTOCEINTJS Lyon and Casseday. 



1859. Lyon and Casseday. Am. Journ. Sci. and Arts, xxix, p. 68. 

 1866. Meek and Worthen. Geol. Rep. 111., ii, p. 288. 

 1879. Wetherby. Journ. Cin. Soc. Nat. Hist. (April). 

 1879. Wetherby. Ibid. ( October No, ) . 

 1879. Zittel. Handb. d. Palaeont., i, p. 365. 



Syn. Asterocrinus Lyon, 1857 (not Miinster). Geol. Rep. Ky., iii, 

 p. 472. 



Pterotocrinus was first described in 185T by Lyon under the 

 name of Asterocrinus., which, being previously occupied by Miin- 

 ster, was changed to the former in 1859 by Lyon and Casseday. 



Meek and Worthen, in revising the genus in 1866, indicated in 

 their generic formula four series of interradial plates, which is 

 evidently a mistake, as that order of plates is entirel}^ absent in 

 the calyx. They further changed the term " wings or lobed 

 pieces " of Lyon into " interbrachial appendages," 



In 1879, Prof. Wetherb}^, who had obtained very perfect speci- 

 mens from Kentucky, published some new and interesting obser- 

 vations on the genus, and described in the April and October 

 numbers of the Journ. of the Cincin. Soc. Nat. Hist., three new 

 species. He considered the small plates which had been recog- 



