oUo 



processes indicate the attachment of ribs, which were rendered 

 probable by the apparatus for breathing by inspiration, (in this 

 respect differing from the frog, and approaching the crocodile ;) 

 the presence of ribs, too, says Prof. Owen, implies that their 

 generative economy was similar to that of existing crocodiles. 

 A bone resembling the episternum of the Ichthyosaurus, with 

 deep and wide grooves, indicates the existence of clavicles; in 

 this, differing from the crocodile and resembling the frog. The 

 humerus, radius, ulna, tibia, and bones of the toes, are eminently 

 Batrachian in their characters. The pelvis resembles that of the 

 crocodile in the articulation of the ilium with the ends of two 

 thickened and expanded transverse processes, instead of one^ as 

 in the frog ; and in most other respects it is Batrachian in its 

 character. The great size of the acetabular cavity shows the 

 same relative superiority in the size of the hinder extremities as 

 in many Batrachians ; this greater size of the hind feet compared 

 with the fore feet is seen in all the footprints of Cheirotherium. 



Osseous dermal scuta or plates have been found in connec- 

 tion with these bones, showing crocodilian affinities ; but their 

 presence, as Owen says, would not absolutely exclude the 

 Labyrinthodon from Batrachians, as the skin is the seat of the 

 variable characters in all animals ; the Labyrinthodon would 

 not, in this respect, be much further removed from Batrachians, 

 than is Trionyx from ordinary Chelonia. 



The Labyrinthodon resembles fishes in the absence of any 

 trace of alveoli of reserve for the successional teeth, — in the 

 anchylosis of the base of the teeth to distinct and shallow sock- 

 ets, — and in having a row of small teeth anterior and external to 

 the larger. 



For other and further details of the resemblances, both Batra- 

 chian and Crocodilian, in the genus Labyrinthodon, we must 

 refer to Mr. Owen's paper, of which there is an Analysis in the 

 "Annals and Magazine of Natural History," Vol. VIII. (Lon- 

 don, 1852: pp. 305-13.) 



This Sauroid Batrachian, then, as far as the head is concerned, 

 had the facial and nasal parts of the skull formed after the Croc- 

 odilian type, with Batrachian characters, well marked in the 

 intermaxillary, superior maxillary, and inferior maxillary bones, 

 and in the occipital condyles. 



