270 Messrs. Hancock & Atthey on Reptile- and Fish-Remains 
Besides the above, we have also obtained from the same loca- 
lity portions of three other mandibles: one-belongs to the left 
ramus, and is in a bad condition; two are in a good state of 
preservation, but, unfortunately, they both represent the same 
portion of the right ramus, the anterior es of each being 
wanting, as also the proximal extremity. They each measure 
about six inches in length, and widen a little backwards, where 
they are two and a half inches broad. If we add to the length 
of these fragments that of the anterior portion before described, 
and allow for the parts that are wanting, it would appear that 
the ramus could not be less than twelve or thirteen inches 
long. The internal cartilage having been removed, the lateral 
bony walls have collapsed and are inclined inwards. The jaw 
is consequently comparatively thin and flattened. The external 
surface exhibits the peculiar ornamentation in a very beautiful 
manner. It is the same as on the other bones, the sculpturin 
extending over the whole surface in the form of smooth ele- 
vated ridges composing an irregular reticulation, with the 
meshes or depressed spaces deep and of various forms, fre- 
quently agile sometimes rounded, but most commonly 
elongated; so that the reticulated ridges, on the whole, have a 
somewhat dendritic appearance. This striking embossed or- 
nament closely resembles that of Labyrinthodon leptognathus 
and L. pachygnathus; only it is considerably finer*. ‘Phe 
inner surface of the bone is smooth, as well as the external 
border of the alveolar ridge; and there is a groove along the 
lower margin extending the whole length of the fragment. — 
The teeth exhibit very distinctly on the upper portion or 
crown the wide, compressed, sharp cutting-edges, and on the 
base the strong fluting or grooves. In several the points are 
quite perfect, and are decidedly lancet-shaped. The teeth are 
anchylosed to the bottoms of shallow pits in the not by any 
means deep alveolar groove. | 
In one of the fragments there are seven teeth; in the other, 
four perfect and three imperfect. In the latter the anterior 
tooth is a little more than half an inch long, and the others 
gradually diminish in size backwards, and are placed consider- 
ably apart from each other, the spaces between them being 
nearly three-eighths of an inch wide. In the other fragment 
the four most perfect teeth appear to be situated at the poste- 
rior extremity of the alveolar groove, though the jaw is con- 
tinued for a considerable distance behind them. ‘The anterior 
of these four is not quite half an inch long, and the others 
diminish gradually in size posteriorly, the last being not much 
* See Prof. Owen’s paper, Trans, Geol. Soc. ser. 2. vol. vi. pls. 45, 46, 
