BY R. ETHERIDGE, JUN. 407 



bend inwards to above the cavity of the external gi-oove ; thence 

 it bends outwards to become the median surface for union with 

 that of the left pre-maxillary. The inner alveolar wall descends 

 at last four-eighths of an inch lower than the outer one. There is 

 no indication of the nasals. In the lower jaw the lower portion of 

 the dentary is not preserA^ed, having flaked-ofF from the specimen, 

 but this bone would probably present a deeply sigmoidal outline if 

 whole. It now measures through the base of the alveolus 1^ 

 inches, the latter being six-eighths of an inch deep. From 

 the bottom of the alveolus thi'ough the inner portion of the dentary 

 there is only a thickness of three-sixteenths of an inch. The 

 upper element of this bone is nearly as correspondingly thick as 

 the lower portion of the pre-maxillaiy, whilst that part below the 

 alveolus, including the portion split off is at least one inch in 

 height. The external longitudinal groove leads into a sac, which 

 with the passage uniting the latter to the outer groove almost 

 completely cuts the bone in half, and strongly resembles the 

 similar vascular canal ia the pre-maxillary. We also notice in 

 this section the difference in the angle of the alveolus in the upper 

 and lower jaws, and doubtless the curved outline of the lower 

 teeth is a provision of nature to bring them into apposition with 

 those of the upper jaw, whicli are straighter and set at an entirely 

 different angle. 



I do not see any trace of the splenial bones, the fracture which 

 severed this portion of the jaws from the remainder of the head 

 having taken place too far forward ; unless the small fragment of 

 bone at the very bottom of the section, in the middle line, 

 represents the anterior termination of the right splenial. 



Since Prof. McCoy's first announcement of Enaliosaurian 

 remains in Queensland, very little seems to have been done 

 towards working out the distribution of this important group 

 of Reptiles in Australia. The details of his Ichthyosaurus 

 Australis given by McCoy are so meagre, that it is with the 

 greatest difficulty a comparison can be instituted with any other 

 remains. The presence of the casts in the Australian Museum 

 would have rendered this task easier than it otherwise could have 



