Natural History of the River Trout. 165 



round black spots ; dorsal, anal, and ventral with 

 a black and white outer edge. 



Hab. " Iceland, North Britain, Ireland, Scandi- 

 navia. D. 13-14, A. 11-12, P. 14, V. 9, L. lat. 

 120, L. transver 27-30/002. pyl.' 33-46, Vert. 59-60. 



" (b) Salmo fario ausonii. The common River 

 Trout. 



" Attaining to a length of thirty inches ; female 

 mature at a length of eight inches. 



" Head well proportioned to its shape ; body 

 rather stout. The posterior point of junction of 

 operculum and sub-operculum is midway between 

 the upper end of the gill opening -and the lower 

 anterior angle of the sub-operculum. Praeoperculum 

 with a not very indistinct but very oblique limb ; 

 snout rather produced in the male, the lower jaw 

 having a hook in front in very old examples only. 

 Maxillary much longer than the snout, very strong, 

 and dilated ; it extends to below the hinder margin 

 of the orbit already in specimens of eight or nine 

 inches in length. Dentition strong. The head of 

 the vomer is triangular, much broader than long, 

 with a transverse series of teeth across its base ; 

 body of the vomer with a double series of strong 

 teeth, the teeth being placed either opposite each 

 other or alternately; this series of teeth is per- 

 sistent throughout life. Fins comparatively short, 

 and rounded ; the length of the pectoral is one-half 



