from the Shales of the Northumberland Coal-field. 271 
more than half that length; but its extremity is not quite 
erfect. The three imperfect anterior teeth are very much 
arger than the four posterior ones ; the largest of them, which 
is the centre one, cannot have been less than an inch in length 
and three-eighths of an inch wide at the base. They are all 
placed considerably apart from each other; but they are not 
quite so widely separated as those in the other fragment. 
We have two other fragments of jawbones of this reptile ; but 
. they are in such an unsatisfactory condition that not much can 
be said about them. One of them, however, is probably a 
maxillary bone; it is six and a half inches long, and an inch 
and a half wide; but it is so imperfect that its form is not 
determinable, and it is much encumbered with other bones. 
A portion of the alveolar border is nevertheless distinctly dis- 
played, with five close-set teeth, the largest of which 1s up- 
wards of half an inch long. Other fragments of teeth are 
scattered about. We have also a confused mass of apparentl 
-eranial bones, which show the peculiar surface-sculpture. A 
. of a jaw with a tooth or two is mixed up with these 
ragments. 
For some time these portions of mandibles were all sup- 
posed to belong to Rhizodus lanceiformis, Newberry, as the 
teeth attached to them are undoubtedly similar to those of 
that reputed fish. But on considering that the sculpture of 
the bone-surface is exactly like that of the cranial and pre- 
maxillary bones, that the teeth of the latter are similar to 
those of the mandibles, and that the teeth of both exhibit pre- 
cisely the same Labyrinthodont structure when Ree in 
transverse section, the conclusion that these mandibular frag- 
ments. really belong to this new Labyrinthodont is quite irre- 
sistible. ‘The piscine nature of R. lancetformis is therefore 
questionable. Certainly the teeth usually so designated be- 
long to this reptile ; and unless other evidence be forthcoming, 
this reputed species of RAzzodus will have to be erased from the 
list of Carboniferous fishes. 
The two sets of sternal plates are characterized by the same 
surface-ornament which we have found on the other bones; 
and though neither of them is perfect, sufficient is preserved 
to enable us, by the aid of both, to form a very good idea of 
their shape and characters. In the finer and larger specimen, 
all the three plates are present, and by their position exhibit, 
though considerably displaced, their relation to each other. 
The posterior ends of the two lateral plates lie in juxtaposition, 
overlapping the anterior portion of the central plate, and di+ 
verging backwards; a portion only of the posterior margin 
of the central plate is exposed. By removing the matrix, 
