BATOCEmiDiE. 397 



to the foot of the pahnars ; the latter slightly projecting outward. Surface 

 of plates elevated ; the radials raised into conspicuous transverse nodes ; the 

 brachials keel-shaped, forming angular ridges, which branch to the bases of 

 the arms ; the first interbrachials tumid, the succeeding ones almost flat. 



Base moderately high, notched at the sutures ; the lower edges project- 

 ing laterally, and forming a well defined rim ; the bottom rather deeply 

 excavated for the reception of the column. Eadials very large, three times 

 as wide as the first costals ; the latter unusually small and quadrangular ; 

 the second costals somewhat larger and pentangular. Distichals 2 X 2, of 

 the size of the costals. Palmars 2X4, in contact laterally, except at the 

 posterior side where they are generally separated by a small interbrachial 

 piece. Arm openings nearly equidistant, only the space between the two 

 posterior rays being a little the widest and slightly depressed. Arms long, 

 slender, incurving, subcylindrical to one third their length, then gradually 

 flattening and expanding to once and a half their lower width; their sides 

 knife-like and serrated- along the edges. Interradial spaces somewhat 

 depressed ; the first interbrachial very large, supporting two small plates 

 in the second row. Anal plate a little higher than the radials, and formed 

 into a circular node instead of a transverse one ; followed by three, two, and 

 one plate. Ventral disk hemispherical, somewhat bulging toward the sides. 

 Plates large and slightly convex. Between the plates at the periphery there 

 are upon the surface narrow but deep vertical grooves, which lead to the 

 respiratory pores. The pores are large and arranged in the usual manner. 

 Anal tube excentric, very long, stout, retaining the same width to near its 

 upper end, where it tapers rapidly and is pierced by a minute opening. At 

 about half its length, it curves abruptly at right angles, and passes out 

 laterally between the sides of the arms. Column moderately large, com- 

 posed near the calyx alternately of thicker and thinner joints. 



Horizon and Locality. — Lower part of the Upper Burlington limestone, 

 Burlington, Iowa. 



Types in the University Museum at Ann Arbor, and in the Museum of 

 Comparative Zoology. 



Remarks. — The peculiar structure of the anal tube, to which we allude 

 in the description, occurs in all our specimens, and has been observed also in 

 a fine specimen in the Museum at Cambridge. 



Hall, in his Preliminary Descriptions of New Crinoids, p. 14, mentions 

 a form to which he applied the name Actinocrinus matida, var. attemtata ; but 



