412 THE CKINOIDEA CAMERATA OF NORTH AMERICA. 



oral projecting and three times as large as the four others, forming the base 

 of the anal tube at its anterior side. 



Horizon and Locality. — Keokuk group; Keokuk, Iowa, and Nauvoo, Ills. 



Type, in the (Worthen) Illinois State collection, Springfield. 



Memarhs. — This species agrees fundamentally with E. Clmstyi, but has a 

 much larger number of interbrachials, and numerous interdistichals and inter- 

 palmars, which are unrepresented in E. 'Cliridyi, and a much greater expan- 

 sion of the rim. It also differs in having a large axillary palmar, and forty 

 well defined arm openings around the calyx ; while E. Cliristyi with the 

 same number of arms has but twenty openings, a minute axillary, and two 

 arms from each opening. Phylogenetically E. jjlanodiscus is a more adult 

 form of -E". Christyi, but from a classificatory standpoint must be regarded as 

 specifically distinct. The development of the rim from E. Christyi with its 

 twenty arm openings and double arms, through E. trochisciis to E. jjJano- 

 disciis, with its forty independent ai'm openings, was coincident with the 

 geological succession of the three forms. 



Eutrochocrinus Lovei W. and Sp. 

 Plate XXIX. Fig. 7, and Plate XXXII. Figs. 2a, h. 



1881. Batorrimis Lovei — W. and Sp., Revision Talfcocr., Paii; II., pp. 47 and 168. 

 1890. Batocriims Lovei — S. A. Milieu; Nortli Amer. Geol. and Palseont., p. 228. 



In its general habitus very closely resembling Eutrochocrinus CJiristyi, but 

 a smaller species and differing essentially in the arm structure. Calyx wider 

 than high, tapering abruptly to the poles, the sides convex. Plates without 

 ornamentation, flat in the dorsal cup, convex on the ventral disk. 



Basals forming a large conical cup, of which the lower face is occupied 

 completely by the column. Eadials larger than both costals together, about 

 as long as wide, a little widest at the top. First costals small, quadrangular, 

 twice as wide as long ; the second somewhat higher ; their sloping upper 

 faces forming a right angle. Distichals and palmars in two rows of two 

 plates each ; the latter larger than the former, and the arm-bearing second 

 palmars wider than any of the other brachials. Arm openings eighteen 

 to twenty, narrow, directed slightly upwards, and arranged in groups of 

 four — two in the anterior ray — with a shallow depression between the 

 rays. Arms eighteen to twenty, single, short but somewhat larger than in 

 E. Christyi ; composed from their bases up of two rows of very short pieces. 



