MELOCRINID&®. 321 
Dolatocrinus excavatus W. and Sp. (nov. spec.). 
Plate XXV. Fig. 1, and Plate X XVI. Figs. 7 and 8. 
A very large species. Dorsal cup shallow-basin shaped, three times as 
wide as high; the bottom flattened to the top of the costals; the sides 
convex, rapidly curving upwards, a little constricted at the arm bases; the 
radials formed into a deep, sharply pentangular, funnel-shaped pit, which 
penetrates the calyx almost to the height of the arm regions. Surface of 
plates — except those in the pit — covered with parallel ridges, radiating 
from the centre of the plates to their sides, where they meet with similar 
ridges from adjoining plates. In addition to these ridges there are keel-like 
projections following the radials and costals, which grow more conspicuous 
downward, and at about the top of the radials are produced into a tubercle, 
which projects into the funnel-shaped pit, and gives its upper margin a 
slightly stellate outline. Occasionally the carinate ridges are continued to 
the higher brachials, but, as a rule, they become obsolete above the second 
costals. Suture lines slightly grooved. 
Basals elongate ; forming together with the radials a highly elevated 
inverted cone with a large pentalobate canal. Radials large, once and a half 
as long as wide; four fifths of the plates taking part in the pit, the other 
fifth bending abruptly outward ; upper sloping faces short; the lower faces 
equal to one half the greatest width of the plates. First costals small, twice 
as wide as long, their upper and lower faces convex. Second costals wider 
than long and slightly wider than the first. Distichals four; the first as 
large as the two costals together. Arms two to the ray, about equidistant. 
First interbrachial slightly curving, larger than the radials and first costals 
together, elongate, widest across the middle of the plate; angular at both 
ends; the lower end bending inward so as to form a part of the pit. There 
are two large plates in the second row, three smaller ones in the third, and 
these are succeeded by a row of six elongate pieces in the ventral disk, and 
two additional larger plates which abut against the orals. Interdistichals 
one or two in the dorsal cup, followed by five or six small pieces in the 
tegmen, and a larger one between the secondary radial dome plates. Slits 
six to each interradial space, and four to each interdistichal one. Ventral 
disk depressed, slightly tumid; the interambulacral spaces flattened, and 
sometimes a little depressed, producing indistinct ridges along the ambulacra. 
41 
