LABYRINTHODONTIA 189 



milloid form of tooth, whereas all the teeth of the reptile so 

 called are originally, and most of them are permanently, of a 

 cuspidate and not of a mammilloid form ; secondly, because 

 the second element of the word, saurus, indicates the genus to 

 belong to the saurian or lacertian order of reptiles. For these 

 reasons, the writer has proposed to designate the genus in 

 question Lahyrintliodon, in allusion to the peculiar and cha- 

 racteristic structure of the teeth (fig. 67). 



The specimens from British localities are referable to five 

 species — viz., 1. Lahyrintliodon salamandroides ; 2. L.leptogna- 

 thits ; 3. L. polygnathus ; 4. L. vcntricosus ; and 5. L. scutu- 

 latus ; and we shall here briefly notice the characters exhi- 

 bited by the bones assignable to the second, third, and fifth 

 species. 



Labyrinthodon leptognathus. — The remains of this species 

 consist of fragments of the upper and lower jaws, two vertebra?, 

 and a sternum. They were found in the new red sandstone 

 quarries at Coton End near Warwick. 



A dorsal vertebra from Coton End presents further evidence 

 of the batrachian nature of the Labyrinthodon. It has con- 

 cave articular cavities at the extremities of the body, — a con- 

 dition now known among existing reptiles only in the Geckos, 

 and in the lower or perennibranchiate division of Batrachians. 

 It is a common structure in extinct Saurians, but the depth of 

 the vertebral articular cavities in the Labyrinthodon exceeds 

 that in the amphicoelian Crocodiles and in most Plesiosaurs. 

 The body of the vertebra is elongate and sub-compressed, with 

 a smooth but not regularly curved lateral surface, terminating 

 below in a slightly-produced, longitudinal, median ridge ; and 

 it exhibits the same exceptional condition in the reptilian class 

 as do the vertebras of existing Batrachians, in having the 

 superior arch or neurapophysis anchylosed with the centrum. 

 From each side of the base of the neural arch a thick and si i ■< mg 

 transverse process extends obliquely outwards and upwards. 



