348 PROCEEDINGS OF THE ACADEMY OP [1881. 



We further place here the following new species, which are 

 interesting as all three are of a similar type, and either descendants 

 from each other, or closely related to each other : — 



Eretmoorinus originarius n. sp. 



Body small, calyx and dome of equal height, the former sub- 

 turbinate with nearl}^ straight sides, the vault somewhat inflated, 

 with convex sides. Radial plates covered with an obscure ridge, 

 passing longitudinally from plate to plate, all other plates of the 

 calyx nearly or quite smooth. 



Basal cup low, truncate at the bottom, extending into a ring 

 which projects beyond the rather large column. First radial as 

 large as second and third combined ; the second much shorter, 

 quadrangular, twice as wide as high ; the third as large as the 

 second, and but little wider, the lateral sides almost straight. 

 Secondary radials consisting of two series of plates, which are of 

 a similar form as the two upper primary radials but smaller. They 

 are followed in the anterior ray by the arms, in the four other rays 

 by tertiary radials. In the lateral rays both upper and secondary 

 radials are axillary, and give off 2 X 2 tertiary radials with four 

 arm openings, the two postero-lateral rays have three, of which one 

 side only is bifurcating, while the other remains simple. Arms 

 simple throughout, of medium length, the tips slightly' spatulate 

 and folded inward ; composed of rather high, somewhat convex 

 joints, with comparatively strong pinnules. 



Interradials three, the first very large, with a faint node in the 

 centre ; anals one, three and two. Dome composed of convex 

 plates ; annal tube unknown, but evidently not very large. 



Geological Position, etc. — From the age of the earlier Keokuk 

 limest., near Bono, Lawrence Co., Ind., where the species occurs 

 iu great quantities. Collection of Chas. Wachsmuth. 



Eretmoorinus intermedius n. ^p. 



In form, size, and ornamentation resembling E. originarius, 

 perhaps a little more truncate at the basal portions, and the arm 

 bases more spreading, differing, however, in the arm structure. 

 It has normally six arms from each posterior, and four from the 

 rest of the rays, twenty-four arms to the individual. The radial 

 portions of the calyx, ijj the lateral ra3^s, are unchanged, while 

 the anterior ray has in addition 2X2 tertiary radials, and 

 consequently twice the number of arms. In the posterior rays, 



