450 PALEONTOLOGY OF ILLINOIS. 



GENUS PLATYCKESTTES, Miller. 

 PLATYCRLNTTES TENUIBRACHIATTJS, M. and W. 



PI. 3, Fig. 4. 

 Flatycrinites tenuibrachiatus, MEEK aud WORTHEX. Proceed. Acad. Nat. Sei., Phila., 1869, p. 168. 



BODY rather small, subglobose, being somewhat wider 

 than high. Base shallow, or dish-shaped, with a subpen- 

 tagonal outline, and a rather broad shallow concavity below, 

 nearly twice as wide as the rather small round facet for the 

 attachment of the column. First radial pieces a little wider 

 than high, having a general quadrangular form, but with 

 the superior lateral angles slightly truncated for the recep- 

 tion of the interradial pieces, and the lower sides a little con- 

 vex in outline ; sinus in thaupper side of each equaling about 

 half its breadth, and extending down on the outer side 

 about one-third to one-fourth its length. Sutures channeled 

 by the beveling of the edges of the plates. Second radial 

 pieces very small, wider than long, triagonal in form, and 

 wedging out on each side so as to allow the iirst brachial 

 pieces to come in contact with the first radials at the lateral 

 edges of the sinuses in the same. 



First divisions of the rays, from their origin on the second 

 radial pieces, each round and composed of a single series 

 of somewhat wedge-shaped pieces to the fourth piece, which 

 has a pentagonal outline, and gives origin to two divisions, 

 the inner one of which is smaller than the other and with- 

 out farther bifurcations, being a simple arm, composed be- 

 low, for some little distance, of a single series of wedge- 

 formed pieces, beyond which it passes gradually into a 

 double series of alternating pieces, while the outer divis- 

 ion bifurcates on the second piece, its outer subdivision 

 remaining simple like the inner of the first divisions, al- 

 ready described, and its inner division bifurcates again 

 on the fourth pieces, forming two arms like the others, 

 thus making four arms to each of the two main divisions 



