Wealden Formation of Europe, 159 



The G Solar is popularly called " salmon trout" by the 

 colonists, and is recognised from the first by its smaller size 

 and rows of large round brass-like spots on the sides. The 

 species was separated, by Sir J. Richardson, from the former 

 on account of the differences in the number of the fin rays, 

 the spotting of the body, and the greater diameter of the 

 eye as compared with the length of the head and the distance 

 between the orbits. All these characters Professor M'Coy 

 proved to be merely the characteristics of the young fish of 

 the G. Georgianus. 



The G. Truttaceus of Cuvier was mainly characterized by 

 the posterior edge of the preoperculum not being denticu- 

 lated ; and this also was proved by the demonstration of the 

 characters in several specimens to be a character of the very 

 young of the same species, G. Georgianus, with which it also 

 should, as well as the Perca Trutta of Cuvier, be united. 



The very young when examined alive have the caudal fin 

 yellow with a black margin. These colours fade quickly in 

 spirit or on dried skins, so this colouring noted by Cuvier on 

 a drawing from life of a fish of which he had never seen a 

 specimen, gave. rise to the species Perca margiTiata, which, as 

 all the other characters also are those of young Gentropristes 

 Georgianus, Professor APCoy proposed to consider a synonym 

 of that species, thus reducing, by extensive observations on 

 recent specimens, six supposed species of Australian fish to 

 one. 



Art. XXXVIII— The Wealden Formation of Europe, as 

 Illustrated by the Physical Feaiures of 'Port Phillip 

 Bay. By Thomas Harrison, Esq. 



[Abstract of Paper read Oct. 31st, 1864.] 



The characteristics of the Wealden Formation, in reference 

 to its probable history, its geographical position, geological 

 structure, and the peculiarity of its brackish and fresh 

 water beds, intercalated between two extensive marine for- 

 mations, were briefly and generally described. 



The hypothesis of Lyell, of a gradually sinking delta, was 

 briefly reviewed, and the points noted in which some of the 

 phenomena observed were not satisfactorily accounted for 

 by such a cause. 



