462 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
regions, 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. guinguelobus ; 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- 
ing 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 others, 
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 others. 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. massissipprensis 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 Locality. — Transition bed between the Upper Burlington 
and the Keokuk beds. 
Type in the Museum of Comparative Zodlogy. 
-iklin 
