LABYRIXTHODONTIA 19.3 



contracted in the middle. A portion of a somewhat shorter 

 and flatter bone is bent at a subacute angle with the distal 

 extremity, and resembles most nearly the anchylosed radius 

 and ulna of the Batrachia. 



The femur wants both the extremities ; its shaft is sub- 

 trihedral and slightly bent, and its walls are thin and compact, 

 including a large medullary cavity. The tibias exhibit that 

 remarkable compression of their distal portion which charac- 

 terizes the corresponding bone in the Batrachia ; they likewise 

 have the longitudinal impression along the middle of the 

 flattened surface. Were more of the skeleton of the above- 

 defined species of Labyrinthodon known, they might present 

 differences of subgeneric value. Such differences in the forms 

 and proportions of the skull, and in the form and relative 

 position of the orbits, of specimens that have been discovered 

 subsequently in the triassic sandstones of Germany, have been 

 so interpreted. 



In the Labyrinthodon (Mastodonsaurus\ Jaegeri — the 

 largest of the species — the skull is triangular, the two condyles 

 projecting from the middle of the base ; the sides are straight, 

 and converge to the obtuse apex. The orbits are oval, nar- 

 rowest anteriorly, and are situated nearly midway between the 

 fore and back part of the skull. The nostrils are very small, 

 and are as wide apart as the orbits. 



Labyrinthodon (Trematosaurus) Braunii, Yon Meyer. — 

 The name Trematosaurus was given by Braun to a labyrin- 

 thoclont reptile, in reference to the parietal foramen, at that 

 time deemed to be peculiar to it, but now known to be com- 

 mon to all the family. The genus was founded on an unusually 

 perfect skull discovered in the richly fossil if erous bunter- 

 sandstein of Bernburg. It is about one foot long, and, rela- 

 tively to its basal breadth, it is longer and narrower than in 

 L. Jaegeri, the sides converging at a more acute angle. The 

 orbits are elliptical, situated in the middle of the skull, and 



