— 507 — 
like structure of the lateral vib. The scale impressions, enlarged in 
Fig. 1a, are produced by tubercles crowded and varying in size, but 
provided, in part at least, with punctiform uwmbilicoid scars like those 
on the large laminar tubercles. 
In this specimen, Fig. 1, portions of the fossil are scaled off in the 
region near the midrib, revealing beneath a thin layer of matrix- 
filling, the impression of the opposite suriace or cuticle of the member. 
On this opposite surface, secn as an impression, lower middle of 
Fig. da, the tubercles are very minuteand not very distant. A portion 
of the large-tubercular surface is seen in the upper part of the same 
photographic enlargement. Asin the other fragment, Tig. 3, the side 
with tubercles in relief is slightly concave. Thera appears to be 
nothing but clay matrix-filling between the convex or finely tuber- 
cular and concave or coarsely tubercular surfaces of the fossil. Hence 
we may infer that the opening represents eciler a thin organ or 
appendage in which the upper and lower lamince or cuticles (inte- 
guments?) were not far appart, or a fleshy body in which the soft 
tissue decayed. 
The small fragment shown four times enlarged, in Plate xi, 
Fig. 3, presents the impresion of a portion of the lamina on which, in 
passing to one side, the large tubercles disappear while at the same 
time the lamina becomes distinctly granulose-scaly or finely-tuber- 
culate like that seen in portions of the specimens already des- 
cribed. 
The large tubercles in this example distinetly show the minute 
umbilicoid scar at the prominent apices. 
Theexample, a part of which is shown, natural size, in Pl. Xi, 
Fig. 1, contains an irregular fragment of the cuticle of the type seen 
on the convex or back side of the original of Pig. 1, Plate x, as descri- 
bed above. For convenience I will speak of this integument or cuticle, 
which bears the very small and rather close tubercles, as the «convex» 
cuticle, the cuticle with the large tubercles, on the other surface of 
the organ or member, being called the « concave» cuticle. Which of 
these is dorsal or ventral is undetermined. 
The features of the convex cuticle are shown, enlarged four times, 
from another specimen, in Pl. xi, Fig. 4. The tubercles contrast 
remarkably in size as may be observed by comparing Fig. 4 with 
Fig. 3, both equally enlarged. In the original of Fig. 1, they are 
