256 MEMOIliS OF THE QCEEXSLAND MUSEUM. 



which arc more conformable to the usual type of skull. The various developments 

 of the rostrum in vertebrate crania provide abundant material to illustrate 

 remarkable processes of evolution. 



Matrix. — Professor H. C. Richards, Hon. Petrologist and Mineralogist on 

 our staff, kindly contributes the following note on the matrix : — " Stone-coloured, 

 fine-grained, homogeneous calcareous mudstone. There is sufficient calcareous 

 material to cau'^e rapid effervescence with dilute hydrochloric acid, and a residual 

 mass of cream-coloured clay material is left behind." 



Associated Fossils. — An almost- complete shark's tooth is present in the 

 brecciated mass between the mandibular rami, and is probably an anterior tooth of 

 Lamna appendiculata Agassiz. 



Several specimens of the common bivalve, Aucella liughendenensis Etheridge 

 Mere taken from the matrix, including fairly complete valves from the orbits. Two 

 specimens of a small gasteropod were found, and Mr. W. H. Bryan, M.Sc, Hon. 

 Palaeontologist on our staff, has identified these as Turritella {?) microlinea, a rare 

 shell which was named by Etheridge in 1920.^® 



LIST OF PLATES. 

 Plate XV. 



Figure L — Skull of Ichthyosaurus australis ; superior view. Arppr-Ojdi»e*e4y — Qus-^bird 

 iiatui ' c tl— 8ig«. 



Figure 2. — Skull of Ichthyosaurus australis ; lateral view. Approximately one-seventh 

 natural size. 



Plate XVI. 



Figure 1. — Skull of Ichthyosaurus australis ; posterior view. 



Figure 2. — Anterior section of rostrum, showing disrupted teeth. Approximately one- 

 half natural size. 



28 R. Etheridge, Publ. No. 269, Qld. Gaol. Sur., 1920, p. 13. 



