462 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



reo-ioiis, and not so deeply excavated as in some other species of this genus. 

 Plates more or less tumid, their surfaces smooth ; the suture lines quite dis- 

 tinct. Basals large, longer than in D. mississippiensis, but not overhanging 

 the column so far as in D. quinquehhus ; the sutures grooved. Radials once 

 and a half as wide as long, rather deeply notched at the sides. First costals 

 quadrangular, the sides convex ; considerably wider than long. Second cos- 

 tals generally heptangular, sometimes hexangular ; the sides rapidly spread- 

 ino- upwards ; twice as wide as long. They support in the anterior and the 

 two posterior rays an axillary distichal, and this from each side a moderately 

 long palmar ; the two antero-lateral rays have two rows of two distichals. 

 Arm openings four, two, and four, directed outward. Arms in pairs, rather 

 short, curving, flattened in the upper portions, and so far as seen, their sides 

 without spines. Interbrachials three, the first twice as large as the two upper 

 ones, the latter long and narrow, their upper ends rising to near a level with 

 the bases of the arms. Posterior interradius as wide again as the othei-s, 

 with a low rounded median ridge and a depression at each side. The first 

 anal, which is longer than the radials, is followed by three other anals, of 

 which the lower one is the largest ; all have an interbrachial at each side, 

 those of the lower row being as large as the proximal plate in the other 

 four interradial spaces ; the upper ones narrow, and resting within the de- 

 pression at each side of the anal ridge. Ventral disk high, bulging, covered 

 with six spines, of which the lateral ones in some specimens reach a length 

 of 4 cm. ; they curve downward, and taper gradually to a point. The me- 

 dian spine is straighter and somewhat shorter than the other.s. The anus 

 occupies the middle part of a small, subcircular protuberance, composed of 

 from six to eight pieces ; it opens out laterally, and is placed on a level with 

 the lateral spines. Column extremely large, fully twice as thick as that of 

 D. mississippiensis although that is a larger species; nodal joints long, 

 rounded at the edges, and one third wider than the intervening ones, 

 which are quite short. 



Horizon and Localitij. — Transition bed between the Upper Burlington 

 and the Keokuk beds. 



Type in the Museum of Comparative Zoology. 



