210 PALAEONTOLOGY. 





the new red sandstone of Warwickshire, proved that the teeth 

 from both localities possessed in common a very remarkable 

 and complicated structure (fig. 87* ), to the principle of which, 

 — viz., the convergence of numerous inflected folds of the 

 external layer of cement towards the pulp-cavity, — a very 

 slight approach was made in the fang of the tooth of the 

 Ichthyosaurus, whilst a closer approximation to the labyrinthic 

 structure in question was made by the teeth of several species 

 of ganoid fishes, and by those of Archegosaurus. 



Thus, inasmuch as the extinct animals in question mani- 

 fested in the intimate structure of their teeth an affinity to 

 fishes, it might be expected that, if they actually belonged to 

 the class of reptiles, the rest of their structure would manifest 

 the characters of the lowest order, — viz., the Batrachia, the 

 existing members of which pass, though not by the dental 

 character alluded to, yet by so many other remarkable degra- 

 dations of structure, towards fishes. 



In the same formation in Wirtemberg from which the 

 labyrinthic teeth of the so-called Mastodonsaurus had been 

 derived, more or less complete crania of the same animal 

 were afterwards obtained, shewing the development of a sepa- 

 rate condyle on each exoccipital bone, and a divided vomer, 

 with a row of teeth on each half. The following fossils, 

 from the new red sandstone of Warwickshire, gave additional 

 proof of the batrachoid nature of the genus, with evidence of 

 five species, viz., 1. Lahyrinthodon Jagaeri ; 2. L. leptogna- 

 thus ; 3. L. pachygnathus ; 4. L. ventricosus ; and 5. L. scutu- 

 latus. Additions to the group of Eeptiles so exemplified 

 have since been so numerous that the name of the genus has 

 been successively raised to that of a family and an order. 



The Lahyrinthodon {Mastodonsaurus) Jagaeri is the largest 

 known species, having a skull of upwards of three feet in 

 length, and nearly two feet in breadth. Its limbs might well 



* Owen's Odontography, p. 195, pi. 64. 



