LOWER CARBONIFEROUS ROCKS OF ESKDALE AND LIDDESDALE. 77 
strengthened by a central or marginal thickening and fimbriated near their 
lower extremities. The telson is broad at its base, and tapers rapidly for 
about two-thirds of its length, where it becomes quite narrow. It then 
expands into a small, oblong, fimbriated flap, with which it terminates. At 
the points where the tapering ceases, a pair or perhaps two pairs of short spine- 
like appendages are articulated with it. Length, ? inch to 2 inches. 
Observations.—The above characters have been made out from the study of 
over forty specimens, all of which were collected by A. Macconocuiz from 
Eskdale. The manner in which the animal is preserved shows that it must have 
been broader than deep, for out of the large number in the Survey collection, 
only one is found on its side, Allthe rest are preserved back upwards. When 
this is the case the three central ridges on the carapace appear but as if 
slightly crenulated, and it was only the specimen preserved on its side which 
showed that these were produced into spines which may be seen to be directed 
forwards (fig. 3). This taken together with the forward direction of the walk- 
ing limbs, the overlapping of the pleuree of the second abdominal segment both 
ways, and the overlapping of the pleure of those behind it only upon those of 
the next in succession, shows that this animal used the great tail-like apparatus 
made up of the telson and the flattened appendages of the sixth segment for 
swimming backwards, which is the mode of progression in the recent Macrura. 
It is impossible from the manner in which the specimens are crushed to 
make out the relative position of the antennules and antenne, and the 
maxillipedes are never recognisable. The characters on which the classifica- 
tion of the recent Macrura so much depend are therefore not reliable in the 
present case. The general symmetry of the parts best preserved has thus to be 
depended on for that purpose. This applies equally to the other Crustaceans 
here described. The thoracic segments in many cases show through the 
carapace in the manner described by Messrs Meek and Worrtuen, and R. 
ETHERIDGE, junior, in the species described by them. Fig. 3b exhibits the 
endophragmal system of the thorax very completely. The segments are all 
soldered together except the hindermost. It also shows the gill supports ; five 
or six of these are well seen on one side lying in their proper position. 
The only species already described with which this might be confounded is 
the A. Woodwardi of R. Erurripcex, junior,* my friend and predecessor in 
office, after whom I propose to call the present species. It is very much like 
it in general symmetry, though a much larger creature. It differs from it in 
the large size of its rostrum, which as well as the three central ridges of the 
carapace is produced into spines. It is considerably different in the abdominal 
segments, the third being much the largest, while in A. Woodwardz the last is 
the greatest. In A. Etheridgii, the telson broadens out at the tip while the 
* Quart. Journ. Geol, Soc. Lond., 1877, vol. xxxvii. p. 872, t. 27; vol. xxxv. p. 468, t. 23. 
