from the Shales of the Northumberland Coal-field. 275 
equally large Labyrinthodont, differs considerably from those 
just described. It is not quite four inches long, and near to 
the proximal end it is upwards of half an inch wide ; the sides 
are flattened from before backwards, and exhibit a wide shal- 
low groove from one end to the other. The tuberculum is 
scarcely distinguishable from the capitulum, except by its 
projecting boldly outward from the convex margin of the rib; 
its articular surface is continuous with that of the capitulum, 
forming with it a wide diagonal termination. ‘Thence the mb 
tapers rather rapidly to the distal extremity, which is a little 
recurved. 
Two or three limb-bones have likewise been found, which, 
from their size, probably belonged to this species. One of 
these, apparently a femur, is an inch and a half in length and 
five-eighths of an inch wide at the middle of the shaft, which is 
much compressed from front to back, and is a little arched in 
the same direction ; there is a longitudinal depression extend- 
ing from end to end. The extremities are much expanded, 
and they both appear to have double articular surfaces; that 
which is assumed to be the distal extremity is more expanded 
- on one side than on the other. 
From the shortness of this bone it would seem that the 
limbs of this animal were but feebly developed in comparison 
with the size of the body. 
In concluding this description of the remains of this fine 
large Labyrinthodont reptile, a few words may be desirable on 
its relationship with the generic forms previously known. It 
has been already stated that it is closely allied to Loxomma, 
with which it agrees in having large and probably oblique 
eyes, placed near together and in a backward position. It 
agrees pretty well, too, with it in the general form of that 
assemblage of bones which we have called the cranial shield, 
_ though the curves are more flowing. But the parietals differ 
considerably in shape: in Loxwomma they appear to be simply 
elongated, and scarcely, if at all, enlarged behind* ; while 
in Pteroplax they are much enlarged posteriorly, and the 
frontals seem to be more produced. ‘The sternal plates like- 
wise differ from those of Prof. Huxley’s genus, in which 
the lateral ones are quite short; but in Pteroplax they are 
much elongated, agreeing in this respect with Archegosaurus ; 
and the central plate in Lowomma is devoid of the remarkable 
lateral lobes which characterize that of our genus. 
We have also seen that this new reptile resembles to some 
extent Dasyceps, particularly in the two occipital horns; but 
the small eyes, backward position of the parietal foramen: and 
* Proc. Geol. Soc. vol. xviii, p. 292, pl. 11. 
