412 THE CRINOIDEA 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. 
ftemarks. — This species agrees fundamentally with #. Christyi, but has a 
much larger number of interbrachials, and numerous interdistichals and inter- 
palmars, which are unrepresented in H. Christyi, 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 #. Christyi with the 
same number of arms has but twenty openings, a minute axillary, and two 
arms from each opening. Phylogenetically £. planodiscus is a more adult 
form of L'. 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 £. trochiscus to E. plano- 
discus, with its forty independent arm openings, was coincident with the 
geological succession of the three forms. 
Eutrochocrinus Lovei W. and Spe. 
Plate XXIX. Fig. 7, and Plate XX XIT, Figs. 2a, b. 
1881. Batocrinus Lovet —W. and Sp., Revision Paleocr., Part II., pp. 47 and 168. 
1890. Batocrinus Lovei —8. A. Mituer; North Amer. Geol. and Paleont., p. 228. 
In its general habitus very closely resembling Eutrochocrinus Christyi, 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. Radials 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 
Li. Christyi ; composed from their bases up of two rows of very short pieces. 
