ON CARBONIFEROUS LABYRINTHODONTS 533 
men, exhibiting this median plate with the triangular lateral plates, 
which are connected with its antero-lateral edges in Labyrinthodonts 
mm situ. This specimen is represented in fig. 2. 
The median plate is §$ inches long, by at least 24 inches broad at 
its widest part. Its anterior extremity is broken away, but, I think, 
not for any great extent. Its posterior end (almost entire) is abruptly 
truncated, and ? of an inch wide. It continues of about the same 
width for nearly an inch, and then its edges, becoming thinner, 
sweep outwards with a slight curve until the plate attains the 
maximum width I have mentioned, at a distance of 2} inches from 
its hinder end. Here it becomes so completely overlapped by the 
lateral plates, that no more can be said about its lateral contour. A 
fragment of a somewhat larger plate of the same kind leads me to 
believe, however, that the plate does not attain any much greater 
width anteriorly. The middle of the plate is thicker than its edges; 
and shallow, slightly reticulated grooves diverge from the concealed 
centre of the plate, towards its thin edges, before reaching which 
they are lost. The form of what remains of the lateral plates is 
given in the figure; they are thicker internally and exhibit the 
same radiating grooved sculpture as the median plate. The grooves 
diverge from the middle of the inner margin of each plate. 
2. Description of a new Labyrinthodont (Pholidogaster 
pisciformis, Huxley). 
Loxommia is not the only Labyrinthodont in the Edinburgh coal- 
field. Some years ago a remarkable fossil was obtained from the 
same district by Sir Philip Egerton and the Earl of Enniskillen, but 
as, on mature consideration, it appeared to them not to be a fish, it 
was handed over to the British Museum. My attention was long 
ago drawn to this specimen by Mr. Davis, of that Institution, who, 
at the same time, very justly remarked upon the resemblance in the 
arrangement of the scales between this animal and Archegosaurus. 
A recent careful study of the fossil has fully borne out Mr. Davis’s 
suspicion, and has convinced me that the fossil is an Amphibian allied 
to Archegosaurus, though it differs from the latter in the form of the 
head, the extent to which the ossification of the vertebral column 
has proceeded, and inthe characters of its dermal armour. It shares 
with Archegosaurus, however, the peculiarity of having its over- 
lapping scales arranged in double oblique series between the pectoral 
and pelvic arches only, whence, and on account of its fish-like form, 
