BATOCEINIDiE. 411 



base ; the upper palmars abruptly curving upwards, and deeply excavated 

 to form the arm facets. Ventral disk near its periphery flat or even concave, 

 the plates nearest the margin highly tuberculous, projecting outward and 

 upward. Anal tube stout, composed of heavy plates, which are surmounted 

 by a short central spine. Interbrachials numerous, consisting of from six to 

 eight pieces at the regular sides, and of about eleven to thirteen at the 

 posterior one. There are frequently also from one to two interdistichals. 

 Column composed of large, rather high joints with distinctly convex edges. 



Horizon and Locality. — Burlington and Keokuk Transition bed, Des 

 Moines Co., Iowa, and Nauvoo, Ills. 



Ti/jpe in the Museum of Comparative Zoology. 



Remarks. — This variety forms a transition between Eutrocliocrinus Christi/i 

 and E. planodiscus. 



Eutrochocrinus planodiscus (Hall). 

 Plate XXXII. Figs. 4a, b. 



1S60. ActuiocTmus planodiscus — Hall; Suppl. Geol. Rep. Iowa, p. 45. 



1S73. Batocrinus planodiscus — Meek and Woethen; Geol. Rep. Illinois, Vol. V., p. 367. 



1878. Batocrinus planodiscus — W. and Sp., Proceed. Acad. Nat. Sci. Pliil., pp. 231 and 233. 



1881. Balocrinus planodiscus — W. and Sp. ; Revision Palseocr., Part II., p. 167. 



Of the type of E. Cliristiji, but more closely approaching its variety 

 E. trochiscus, with a greater expansion of the calyx than even in that form ; 

 conical in the lower portions. From the first costals to the third palmars 

 the plates are arranged almost horizontally, the post-palmars decidedly curve 

 upwards. Plates slightly convex, their surfaces smooth. 



Basals as in E. Chrisfyi. The radials comparatively smaller than in that 

 species ; the costals larger, especially the second. Distichals in two ranges, 

 as large as, or larger than, the costals. Palmai's three, supporting two rows 

 of large post-palmars separated by interbrachials, interdistichals, and fre- 

 quently by interpalmars. Arm openings forty, eight to each ray ; support- 

 ing forty apparently delicate arms. According to Hall, the species has 

 fifteen interbrachials in nine ranges, nine to eleven interdistichals, and five 

 to six interpalmars. A specimen in our collection has only from six to 

 seven interdistichals, four interpalmars, and about eighteen plates above the 

 anal piece. Ventral disk depressed, deeply concave, except the median 

 portions, which support the anal tube and are conical. The radial dome 

 plates are more convex and larger than the interambulacral pieces. Posterior 



