PLATYCEINID^. 683 



Platycrinus bonoensis White. 

 Plate LXIX. Fig. 6. 



1878. White; Proceed. Acad. Nat. Sci. Pbila., p. 30; and 1880, U. S. Geol. Surv. Terr, by Eajden, 



Coatr. to PaliEont. No. 5, p. 160, Plate 40, Fig. 5. 

 1881. W. and Sp. ; Revision, Part II., p. 70 (Proceed. Acad. Nat. Sci. Pliila., p. Hi). 



Syn. P. atemdis S. A. Miller, 1891 ; Geol. Surv. Missouri, Bull, i, p. 11, Plate 1, Pig. 8. 

 Syu. P. caiuc.us S. A. Millek, 1892; Adv. Slieets ISth Rep. Geol. Surv. of Indiana, p. 13, Plate 

 2, Fig. 13. 



Closely allied to the preceding species, but having five to six arms to the 

 ray instead of four, and these are proportionally shorter, more closely packed, 

 and heavier. Dorsal cup wider than high, bowl-shaped, a little spreading, the 

 margins of the plates slightly beveled, giving to the central portions a slight 

 convexity. Surface without ornamentation. 



Basals proportionally small, forming a shallow basin, broadly truncated 

 below and excavated at the bottom, the sides somewhat constricted so as to 

 form a rounded projecting edge around the lower margins ; the interbasal 

 suture lines slightly elevated. Radials wider than long, gradually expanding 

 upwards, the upper angles truncated, deeper at the anal side. Facets from 

 one half to two thirds the width of the radials ; semicircular. Costals small, 

 trigonal, rarely covering the full width of the facets, and the distichals abut 

 against the radials. First distichals once and a half as wide as long, the 

 axillary one a little wider and somewhat higher. The latter gives off an 

 arm to the outer side of the ray, and supports at the inner two palmars with 

 two arms, making three arms to each subdivision, or six to the ray, excep- 

 tionally five. The arms are stout, especially in the middle, and quite short ; 

 they are uniserial to the fourth plate, beyond this biserial. Column slightly 

 elliptic, and twisted. 



Horizon and Locality. — Uppermost part of the Keokuk group and lower 

 beds of the Warsaw limestone, Bono, Lawrence Co., Ind., and Boonville, Mo. 



Tt/pes in the collection of W. F. E. Gurley, and E. A. Blair at Sedalia, Mo. 



SUBSPINULOSVS GROUP. 



Basal cup almost as high as the radials, subcylindrical. Surface of plates 

 smooth or ornamented. 



