— ¢€0o1 — 
We have here a portion of a member dividéd into four unequal 
lobes or spines. The larger and longer of these, on the left, has 
narrow elongated tubercles varying in size and crowded so as to 
form a mesh. This structure, including the umbilicoid scars near 
the distal ends of the tubercles, is precisely that seen in the marginal 
rib of the original of Fig. L, on Plate x, and shown enlarged in 
Fig. 1a. It is the impression of the back or large-tuberculate 
(concave) side of the fossil. In the three shorter lobes the near (convex) 
Surface is seen, strongly convex in each lobe. 
On this side, we have, as photographically shown four times 
enlarged in Fig. 2 a, broad irregular crowded tubercles varying in 
size and often interfering. 
The umbilicate scars are large and clear, near the distal ends 
of the tubercles. The interference of the tubercles and their fre- 
quent deformation suggest a slight imbrication. This suggestion 
is supported by the profile of the large spine on the left in which 
the distal prominent points project slightly outward and upward, 
in exactly the form seen in the very small serration at the border 
of the original of Fig. 1, Plate x. 
Mention must be made of the fact that the three connate lobes on 
the right in Fig. 2, Pl. xi, are seen as the upper surfaces of casts, the 
cast material being nearly 2mm thick at the highest points of the 
convex surface. On this convex surface the crowded tubercles, noted 
above, are not in relief; but they are marked by narrow raised boun- 
dary lines, the umbilicoid scars also being in the same relief. 
The back side of the fossil, shown in the lower. part of the speci- 
men, where the cast has been broken away, exhibits the impression of 
the opposite (concave) cuticle with the large type of rather distant tuber- 
cles; i. e, the cuticle on the opposite side of the fossil bore the large type 
of tubercle in relief. This under or nearly fiat side in the specimen in 
hand corresponds exactly to the concave surface with large tubercles in 
the organs or members shown in Figs. 8 and 1, on Plate x, while the 
upper or convéx surface, seen in the short lobes corresponds to the 
convex, small-tuberculate, surface seen in part on Fig. 1a, of Plate x, 
and Figs. 1, and 4. of Plate xi. 
The characters in the specimens described above are in such com- 
plete agreement, the highly varied features being presented by fra- 
gments in organic union, that itis impossible to doubt that all pertain 
5560 65 
