264 PALAEONTOLOGY OP ILLINOIS. 



0.38 inch; breadth, above the middle, 0.42 inch; breadth of 

 base, 0.32 inch; height of do., 0.14 inch. 



This species closely resembles Dicliocrinus simplex, of Shumard (Trans. 

 Acad. Sci., St. Louis, vol. l,pl. ^-,fig- 2), being of the same size, and similar 

 in form, excepting that it is distinctly constricted instead of convex near the 

 middle, while it is proportionally broader above. It is possible these two forms 

 may tre only varieties of one species, but as we have not yet seen any interme- 

 diate gradations between them, we are led to regard them as specifically dis- 

 tinct. 



Locality arid position : Bloomington, Indiana; St. Louis group of the Lower 

 Carboniferous series. 



Genus PLATYCRINUS, Miller, 1821. (See p. 170.) 

 Platycrinus Prattenanus, M. and "W. 



PI. 20, fig. 2. 



Platycrinus Prattenanus, Meek and Worthen, Sept., 1860. Proceed. Acad. Nat. Sci., 

 Philad., p. 379. 



Body below the arms, small, cup-shaped, wider than high, 

 distinctly truncated below by the rather wide, nearly flat col- 

 umnar facet — expanding gradually with convex sides to the 

 summit of the first radials ; composed of comparatively thick, 

 smooth plates, which (excepting in the base) are connected by 

 slightly grooved sutures. Base more than one-third as high 

 as wide, and provided with a small rim around the margin of 

 the truncated under side ; plates firmly anchylosed, and con- 

 nected by subcarinate sutures, the carinse passing down over 

 the marginal rim. First radial plates a little wider than high, 

 quadrangular, nearly as wide below as above, somewhat con- 

 vex in outline, and provided with a rather broad, rounded sinus 

 in the upper margin, for the reception of the second radials — 

 the lower margin of the sinus not projecting on the outer side. 

 Second radial pieces very small or scarcely more than filling 

 the depressions in the first, wider than long, triangular, and 



