AN ICHTHTOSAVEIAN SKULL FEOM QUEENSLAND.— LONGMAN. 2o;i 



The articular is present and evidently rests in its original position on the 

 ■angular, with its outer lateral surface adjoining the surangulare. Only the post- 

 articular area has been freed from the matrix, and this is obliquely set on the 

 angular, with its upper surface turned towards the supraoccipital region. 



The splenials first appear on the lower surface of the mandible at a distance 

 of one-fifth of the length of the skull, this being greatly in advance of the divergence 

 of the premaxillse to expose the nasals in the upper jaw. They are visible for a 

 considerable distance on the inferolateral margin. The relative proportions of 

 these elements are shown in Text-fig. 1. The condition of the fossil does not present 

 evidence for the description of the inner side of the mandible. 



Text-figure 2. — Section showing premaxillary and dentary elements, with teeth fragments, 

 in the poUshed surface of anterior segment of rostrum. Ichthyosaurus auslralis (natural size). 



The internal structure of the anterior end of the rostrum has been demons- 

 trated^by pohshing, and is shown in Text-fig. 2. The alveolar groove has a well- 

 developed inner wall with an expanded margin. On each side of the lower jaw the 

 section exposes a foramen leading from the nutrient groove to the vascular canal. 

 "This section is entirely from premaxillary and dentary elements. 



Teeth. — Unfortunately there are no complete teeth in situ but, as previously 

 ated, remains have been preserved adhering to external surfaces. Som'e of these 



