394 DR. J. E. GRAY ON STERNOTH^RUS. [Apr. J, 



Sternoth.erus. (Figs. 1, 2, 3, 4, & 5, p. 393.) 



Skull very depressed, triangular, very broad, expanded, and swollen 

 behind, as wide just before the tympanic cavity as from the front 

 edge of the upper lip to the condyle. 



Crown flat, with the marks of the sutures between head-shields well 

 impressed, tapering on each side from the back edge of the zygoma to 

 a narrow central prominence. Zygoma very strong, broad, and much 

 bent out and convex, leaving a very large space on each side for the 

 temporal muscle, and entirely enclosing the. circular deep tympanic 

 cavity. Beneath flat, wide, with a very large reflexed edge to each 

 pterygoid bone, and a large hole in front of it, en the outer side of 

 each palatine, on a level with the front of the zygomatic arch. The 

 internal nostrils united, very large, triangular, with a long depression 

 behind them, as broad as their hinder edge, with a slight central lon- 

 gitudinal prominence. The alveolar surface broad, becoming broader 

 behind, with a deep circular central pit in front, for the reception of 

 the point of the lower jaw, and a slight lateral ridge, which com- 

 mences at the back edge of the central part and extends to the 

 middle of the hinder part of the alveolar surface. The outer edge of 

 the upper jaw sharp, bent in, and forming a deep notch on each side 

 of the central part, which is square and prominent. The orbits 

 are oblong, longitudinal, the nose being about half the length of 

 the longitudinal diameter of the orbit. The nose-hole large and 

 square. 



The lower jaw depressed, strong, acute, and bent up in front, 

 rounded beneath in front, and truncated behind at the gonyx, this 

 part being covered by the horny beak as far as the hinder truncated 

 edge. The sides strong, oblique, flattened. The alveolar surface 

 flattened, slightly concave, with a sharp raised outer and inner edge, 

 and with a triangular surface behind the centre, extending as far 

 back as the truncated gonyx, separated, as is also the under part 

 of the jaw, from the alveolar edge by a longitudinal groove for a blood- 

 vessel or nerve, entering just before the condyle. 



The skull is 2| inches from nose to condyle, 2 ( V from cheek to 

 cheek. 



This sliull differs from that of Pelomerhisa, figured by Dr. Waglcr 

 in his ' Nat. Syst. Amphib.' t. ii. figs. 36-4-!, in being much broader 

 and more depressed, and in having more developed zygomatic arches, 

 and in being more swollen out at the sides, especially behind, also 

 in the nose-hole being more erect and slightly hooded over by the 

 nasals. The lower jaw is very similar ; but the front part of the centre 

 of the alveolar surface is much more produced and bent upwards, and 

 the part of the centre behind the alveolar surface is more produced, 

 concave, and truncated, while in Pehmedusn it is much narrower 

 and regularly rounded. 



It is to be observed that Dr. Wagler does not figure the alveolar 

 surface of this species. The tympanic cavity is oblong in Pelotnedusa, 

 and the edge much more sinuated between the tympanic cavity and 

 the end of the upper jaw. 



