28 LARVIFORM CRIXOIDS 



'J he surfaces of the plates are smooth and the calyx is entirely un- 

 ornamented. 



Remarks. — This species most closely resembles K. illinoisensis with 

 which it is associated but is easily distinguished by the smaller size, the 

 narrower rounding of its radials, and the fact that the greatest width is 

 attained near the upper border of the radials. 



Occurrence. — The holotvpe and several other specimens were obtained 

 from shale immediately underlying the Piasa limestone near the center of 

 the NE. % sec. 25, T. 8 N., R. 10 W., Jersey County, Illinois. 



Genus AIDEMOCRINUS' J. M. Weller, n. gen. 

 Genotype Aidemocrinus odiosus J. M. Weller, n. sp. 

 This genus is introduced to accommodate a single species of tiny armless 

 crinoid whose calyx is composed of three rings of plates without a lateral 

 anal opening. It is tentatively assigned to the family Allagecrinidae. 



Aidemocrinus odiosus J. M. Weller, n. sp. 

 Plate II, figs. 5a-b 

 Description. — The calyx is very small. The height of the holotype, 

 which is .55 mm., is equal to about one and one-third times the greatest 

 width. Although the sutures are not shown as clearly as might 

 be desired there can be little doubt concerning the structure of the 

 calyx. It is composed of three rings of plates which are inter- 

 preted as, (1) a basal disc. (2) five equal radials, and (3) an oral 

 FlG 3 dome of five subequal plates. The calyx is subpyramidal and 

 tion^of^the rises from the moderately sized proximal stem facet to the gently 

 ture'of'ilid- convex distal surface. 



e o(Hosus" S The basal disc makes up about one-eleventh of the total height 



wuh rn pi ar fi, of the calyx. Its proximal surface is occupied by a circular stem 

 facet having a diameter equal to about one-third of the greatest 

 width of the calyx, and pierced by a single small central opening. The basal 

 disc rises nearly vertically from the stem facet to its upper edge which is 

 gently scalloped for the reception of the radials. 



The radials form about two-thirds the height of the calyx, are about 

 twice as wide above as below, and about twice as long as the greatest width. 

 They are subovel below and above they are apparently more sharply truncated. 

 The upper edges of the radials are not very well defined, but the corners 

 appear to be rounded off. meeting in gently concave depressions in which 

 the orals rest. A rounded longitudinal ridge is developed down the center 

 of each radiak This ridge is beveled above producing a triangular area 



* aiGrnucv, bashful. 



