LOWER CARBONIFEROUS ROCKS OF ESKDALE AND LIDDESDALE. 87 
of their being so. No sessile eyes have been observed on the carapace, neither 
has a trace of anything been observed that could be construed into such. The 
nature of the other cephalic appendages preserved is quite that of the decapods, 
and the same is the case with the tail (see figs. 10-10¢). The general appearance 
of the thorax and abdomen much resembles the Isopods, but this is only seem- 
ing. Nothing can be said of the walking feet or those of the first five abdominal 
appendages, as in no specimen yet obtained have these been preserved in a 
state to be studied, though in some cases there is a faint appearance as if of 
something of the kind. 
In the specimen represented by fig. 106, which is among the few that has 
been fossilised on its side, the appearance of several segments shows through the 
carapace. The lobe of the carapace is wrinkled with lenticular sigmoid mark- 
ings which may possibly represent the gill arches showing through. It also 
overlaps the pleura of the first thoracic segment so as to entirely hide it, which 
lends additional strength to this supposition, as it indicates how free it is. As 
far as the present specimens go to show the affinities of these small crustaceans, 
I am inclined to the belief that they are lowly decapods, somewhat like the 
opossum shrimp (Schizopods), though not necessarily identical with them. For 
comparison, I have reproduced the figures which Messrs Merk and WorTHEN 
give of their P. typus in the Memoirs of the Geological Survey of Illinois, vol. i1, 
pl. xxxii. Fig. 10 is fossilised back up, as most of ours are. In it thirteen seg- 
ments are shown in the combined thorax and abdomen, but the depressions which 
appear to form the first do not meet in the middle, I am inclined to look upon 
it as belonging to the head, and the sulci as analogous to those seen in the 
head of our specimens. The same may be said of fig. 10g. Ifthat be the case, the 
number of segments in each is the same. The American specimens seem to be 
preserved more in the round than the present ones, hence their generally 
narrower appearance and their not exhibiting the lobes of the carapace. Fig. 
10/ is the restored tail of P. typus, alongside which, fig. 10e, a restoration of 
that of P. Scoticus, from the study of more than twenty specimens, is put for 
comparison. 
As far as I am aware, this is the first species referable to the genus Paleo- 
caris that has been procured from British strata. 
Note 1.—The study of the tails of the macrurous decapods, described in the 
present paper, tends to confirm the opinion of those who hold that the telson 
in the Macrura is only a modified body segment, for all the telsons that are suf- 
ficiently well preserved to retain them have two small swimming flaps cr spines 
articulated with them on each side. These appear to be modified appendages 
and probably represent the exopodites and endopodites of those of the 
other segments. Even the lowly Palwocaris exhibits these articulations. 
