71. CONTRIBUTION TO 



leaves little doubt in the writer's mind that the Warsaw beds are the top of the 

 Keokuk group and not the bottom of the St. Louis limestone as usually consid- 

 ered. 



The specimen figured was obtained from the Keokuk group at Edwards- 

 ville, Ind., by G. K. Greene, and is now in his collection. 



MEGISTOCRINUS CORNIGER, N. Sp. (Rowley.) 



Plate 24. Figs. 1-2-8-4. 



Dorsal cup hardly as deep as the ventral cup with a width about three 

 times the depth. 



The concavity involving the basals and first radials and the flattened zone 

 outside, even the middle of the third radials, give to the dorsal cup a decided 

 basin shape. 



The three basal plates form a hexagon. The first radials are hexagonal. 

 The second radials of about the same size and likewise hexagonal. The third 

 radials are bifurcating plates of seven sides and a little larger than either the 

 second or first radials. The first interradials (interbrachials of W. and S.) are 

 hexagonal and a little smaller than the first and second radials, being a little 

 longer than wide. Two slightly smaller hexagonal plates rest on each of these 

 first interradials. 



The first anal plate is in line with the first radials and hardly less than 

 they are in size. 



Above this latter plate are three somewhat smaller anal interradials, 

 higher plates can hardly be made out on the specimen, but are such as in other 

 species of the genus. There are sixteen arm-bases and apparently thirty-two 

 respiratory pores, two to each arm opening. Owing to the character of pres- 

 ervation these pores can be made out in one or two places only. 



The plates of the ventral disk are small, but the sutures are indistinct. 



The anal opening is eccentric, rather large and somewhat elevated. The 

 plate at the junction of the ambulacral furrows and the central dome plate, 

 each bear a short, strong spine, six in all. 



The calix plates, apparently flat, or very slightly convex in places, and are 

 ornamented by low, fine concentric lines. This species is a little higher, less 

 spreailing, and less lobes ^'at the arm bases, than Megistocrinus Expansus of 

 Miller and Gurley, and with much greater va^lt spines. The plate ornamenta- 

 tion is also apparently difierent. 



The type came from the upper Devonian beds, near Charlestown, Ind., 

 and belongs to the cabinet of Mr. G. K. Greene. 



