CRINOIDS. 205 



appears to be the same form, though the figure given in the 

 Illinois report is somewhat faulty. S. A. Miller's recently de- 

 scribed D. parvulus also seems to be identical with Oasseday 

 & Lyon's form. 



Dichoerinus blairi Millkk. 



Plate XXV, fig. 7. 



Dlchoc7-inus hlairi Miller, 1891: Geol. Hur. Indiana, 17th Ann. Rep., adv. 

 sheets, p. 36, pi. viii, fig. 12. 



Closely related to D. fious, but with four arms to the ray 

 instead of only two. 



Horizon and locality. — Lower Carboniferous, Keokuk 

 limestone : Boonville. 



Talarocrinus simplex ( Shumard). 



Plate XXV, fig. 6. 



Dichoerinus simplex '^YmvadH A, 1857: Trans. St. Louis Acad. Sci., vol.1, 



p. 74, pi. i, figs. 2a-b. 

 Dichoerinus simplex Hall, 1858 : Geology Iowa, vol. I, p. 654, pi. xxiii, 



figs. 12a-b. 

 Dichoerinus simplex Wachsmuth & Springer, 1881 : Proc. Acad. Nat. Sci., 



Phila., p. 258. 



Dorsal cup small, ovoid, smooth externally, and almost 

 indistinguishable from that of a Dichoerinus. Other parts as 

 yet unknown. 



Horizon and localities. — Lower Carboniferous, Saint Louis 

 limestone: Ste. Mary. 



Although only the dorsal cup of this species is known, 

 other forms have been described showing that in the ventral 

 structure Talarocrinus is very different from Dichoerinus. In 

 the first genus the ventral side is very high, composed of rela- 

 tively large plates which are often spiniferous, and the anal 

 opening is a mere aperture in the test. In the second group the 

 calyx above the radials is low, the plates small and the ventral 

 aperture at the end of a short elevation. 



