196 LABYRINTHODONTS. 



each vomer, at the fore part of both the outer and inner rows of the 

 smaller teeth in the upper jaw ; and two or three similar tusks are 

 implanted, somewhat irregularly, behind the anterior extremity of 

 the series of smaller teeth in each ramus of the lower jaw. This 

 allocation of teeth in a double series on the premandibular bone is 

 peculiar, among Reptiles, to the Cecilia and the present almost equally 

 aberrant form of Batrachian. It is a common dental character in 

 the class of fishes, and its repetition in the Labyrinthodon betrays a 

 tendency to the ichthyic type which is manifested by some other 

 of the extinct reptiles, as the Ichthyosaurus, although this genus in 

 its general organization is essentially related to a higher order than 

 that to which the Labyrinthodon belongs. 



The first discovered fossils belonging to this genus were certain 

 detached teeth from the Keuper sandstone (Alaunschiefer) of Wirtem- 

 berg, of which the largest is figured at PL 63, fig. 1, from the " Fossile 

 Reptilien in Wurtemberg," 4to. 1828, of Prof. Jaeger, by whom the 

 name Mastodonsaurus was applied to these teeth under the impres- 

 sion that they were the remains of some gigantic Saurian reptile. (I) 



Other fossil fragments of jaws and teeth, or casts of teeth, also 

 from the Keuper formation, (Dolomitsandstein) , on which Prof. 

 Jaeger has founded his genus Phytosaurus, I believe to belong to the 

 same genus and most probably to the same species as the preceding 

 teeth. The most remarkable of these fossils is described as the 

 palatal ourface of the upper jaw, measuring one foot and a half in 

 length, nine inches in breadth at the posterior part and between two 

 and three inches across the narrower anterior part of the fragment. 

 On one side of this fragment there was a series of twenty-seven, and 

 probably of thirty sockets, with very narrow and not quite equal inter- 

 spaces. The anterior portion containing eighteen of these serial 

 sockets, and probably the fractured bases of the teeth, is copied from 

 Prof. Jaeger's work, at PI. 63, fig. 3. At a short distance anterior to 

 the series of smaller teeth, there is a portion of the socket, a, or 



(1) The genus Mastodonsaurus is placed in the Saurian system of M. Hermann v. Meyer, 

 m the Crocodilian family, intermediate between Steneosaurus or Macrospondylus and Crocodilus ; 

 the species on which the genus is founded is termed, after its discoverer, Mastodonsaurus Jae- 

 geri. Palaeologica, 8vo. 1832, p. 107. 



