HEXACRINID^. 763 



Dichocrinus coxanus Woethen. 

 Plate LXXVI. Fig. 9. 



1883. WoETHEN ; Geol. Eep. Illinois, Vol. TIL, p. 313, Plate 27, Figs. 7. 



1885. W. and Sp. ; Revision Palaiocr., Part III., p. 120 (Proceed. Acad. Nat. Sci. Phila., p. 342). 



A very small and slender species of the type of D. ornatus. Calyx ovate, 

 almost pointed at the lower end, constricted across the costals; greatest dia- 

 meter a little above the basi-radial suture. Surface of the plates covered 

 with irregular longitudinal ridges, from three to four to each plate, which run 

 parallel to the lateral borders of the radials, and are continued along the 

 basals to the column. 



Basals as long as the radials; forming a rather high, obconical cup, with 

 a very narrow columnar attachment. Radials longer than wide, their lower 

 faces moderately convex, the lateral faces nearly parallel, the upper margins 

 constricted and to nearly one half their width excavated for the facets. 

 Costals two, very short, forming a syzygy. Arms ten, slender, rounded on 

 the back ; composed of slightly cuneate pieces. Pinnules long. All other 

 parts unknown. 



Horizon and Locality. — J] ^pev part of Keokuk limestone (Crawfordsville 

 division), Hamilton, Illinois. 



Tyjie in the collection of Mr. L. A. Cox, Keokuk, Iowa. 



Remarks. — Dichocrinus ornatus, with which this species lias the closest 

 affinities, has twenty arms instead of ten, the calyx is less contracted at the 

 arm bases, broadly truncated at the lower end, and it comes from a different 

 horizon. 



Dichocrinus pisum Meek and WoETHEN. 

 Plate LXXVI. Fig. 5, and Plate LXXYII. Fig. 10. 



1869. Meek and Worthen ; Proceed. Acad. Nat. Sci. Pliila., p. R9. 



1873. Meek and Worthen ; Geol. Rep. Illinois, Vol. V., p. 441, Plate 3, Figs. 2a, b, c. 



1881. W. and Sp.; Revision Pateocr. Part II., p. 84 (Proceed. Acad. Nat. Sci. Pliila,^ p. 258). 



Of the type of D. plicatus, but the calyx, instead of globular, subquadran- 

 gular in outline, the basal portions more or less flattened, and the sides along 

 the radials but very slightly convex. It also resembles D. Uneatus in the 

 style of ornamentation, but the ridges are coarser and more prominent, and 

 the basal cup proportionally smaller and less conical. Height one fourth 

 less than the width. Plates thin ; the radials covered by from six to eight 



