ON A STALK-EYED CRUSTACEAN 537 
lateral surface of which is convex from above downwards, is narrow 
and apparently truncated in front, but deep behind, its postero-in- 
ferior angle being somewhat produced, but rounded off. It measures 
065 in. in extreme length, 03 in. in extreme depth. The dorsal 
walls of the abdominal soztes, of which only the anterior three or 
four are clearly distinguishable from one another, are large in propor- 
tion to the carapace, having a depth of 03 in., and an antero-posterior 
length of o13 in. The free inferior edges are not clearly defined, 
but their margins seem to have had much the same curvature as 
those of Astacus or Homarus. The first obvious abdominal segment 
is separated from the carapace by an interval, in which | think I 
can trace the remains of the small, true, first abdominal segment, 
not much more than half the size of the others. If this be the 
case, then the dorsal parts of the fifth and sixth somzfes are broken 
away ; and all that remains of the telson and the appendages of the 
Shelch of Pygocephalus (?) from the Coal-shale near Paasley. 
sixth somdte is a broad flat plate, which lies in front of the third 
and fourth abdominal sovzzées. 
I explained in my previous paper the difficulties which I met 
with in endeavouring to understand this part of the body of 
Pygocephalus;and 1 am sorry to say that the new specimen casts 
but little light upon the subject. The appendages are fairly dis- 
played. At the anterior part of the carapace I believe I can dis- 
cern the eye-stalk, which is about o'! in. long, broader at its free 
than at its attached end, and exhibits a depression, which is broad in 
front but narrows behind to a point on the outer side of its distal 
half. This depression appears to result from the more yielding 
character of the integument, that investing the rest of the eye-stalk 
being dense and shining ; and the surface of this softer integument 
is distinctly facetted. The character of the appendage, in short, 
closely agrees with that of the dried eye-stalk of a Podophthal- 
mous Crustacean. Behind and below the eye-stalk the remains 
of the antennule are traceable ; and this is succeeded by the antenna, 
