Labyrinthodon /rom Wanoickshire. 525 



broad lateral cartilages for the attachment of the coracoids. In the Lacertians it 

 would seem that these lateral cartilages were ossified, and the sternum thus con- 

 verted into a large rhomboidal plate. 



In the anourous Batrachia there are clavicles as well as coracoids ; and in the 

 Toad the mesial extremities of the clavicles rest upon the transversely expanded 

 anterior extremity of an episternal bone, which among recent reptiles bears the 

 nearest resemblance to that of the Labyrinthodon, to which genus the present bone 

 most probably belonged. It is represented of the natural size, at Plate XLV. figg. 9. 

 and 10. 



The fossils above described, consisting of a part of the skull and dental system, 

 a dorsal vertebra, and an episternum, prove the Labyrinthodon to have been essen- 

 tially Batrachian, with striking and peculiar affinities to the higher Saurians ; these 

 affinities lead, in the form of the skull and the sculpturing of the cranial bones, to 

 the Crocodilian group ; and in one part of the dental structure, in the form of the 

 episternum and the biconcave vertebra, to the extinct Ichthyosaur ; while in the 

 condition of the bony palate the deviation from its essentially Batrachian character 

 produces a resemblance to the Lacertian type. 



The anchylosis of the base of the teeth to distinct and shallow sockets is a point 

 in which the Labyrinthodon resembles certain fishes, as the Sphyrana : I am dis- 

 posed also to believe, from the absence of any trace of alveoli of reserve for the 

 successional teeth, that these were reproduced, as in many fishes, especially the 

 higher Chondropterygii, which, it may be remembered, formed the Amphibia natantes 

 of Linnaeus, in the soft mucous membrane or gum which covered the alveolar mar- 

 gin, and subsequently became fixed to the bone by anchylosis, as in the Pike and 

 Lophius among osseous fishes. Nor is it extraordinary that the present extinct 

 Batrachian genus should have its relations of affinity thus radiating in different 

 directions, since we find in the extinct reptilian forms of a later epoch, the combi- 

 nation of Saurian characters with Ichthyic vertebrae and extremities. We possess, 

 as yet, no indication from fossils of the structure or form of the locomotive organs 

 of the Labyrinthodon leptognathus. But it is by no means improbable that the im- 

 pressions figured by Messrs. Murchison and Strickland, found on a slab of sand- 

 stone from Shrewley Common, Warwick, are the foot-marks of this very species. 



The learned authors of the paper quoted, state their belief that these footsteps 

 " were formed by an animal probably alUed to the Batrachia." {I. c. p. 318.) They 

 differ from the feet of Frogs in having the outer toe of both the hind- and fore-feet 

 the longest, while in Frogs the second toe is longest : it is moreover evident that 

 the animal possessed a tail. In both these deviations from the Batrachia a cor- 

 responding approach is made to that family of reptiles to which the modifications 

 of the Batrachian characters of the fossils in question have tended. 



VOL. VI. SECOND SERIES. 3 Y 



