Natural History of the River Trout. 163 



(Caldew, Eden) are inhabited by the southern form, 

 whilst the northern one is found in the River Liddel. 

 However, the latter extends as far southwards as 

 Shropshire, where both forms are met with. Both 

 are subject to the same amount of variation, but 

 the northern form appears to remain within smaller 

 dimensions. The coincidence of the difference in 

 the number of vertebrae with the geographical dis- 

 tribution appears to be remarkable enough to dis- 

 tinguish the two forms ; but whether they be 

 regarded as species or varieties is a matter of minor 

 importance. 



" If we keep them separate, the question arises 

 for which the name of Salmo fario should be re- 

 tained. Linnaeus, even if he had been aware of the 

 difference between the northern and southern forms, 

 would scarcely have distinguished them by different 

 names. He formed the names for Scandinavian 

 and German River Trout, referring especially to 

 the Salmonoid described by Artedi, who attributes 

 to it sixty vertebrae. Thus the name of Salmo fario 

 ought to be retained for the northern form, how- 

 ever, in a case like the present, when the boundary 

 line between species and variety is so obscure, I 

 think it more convenient to adopt a nomenclature 

 indicative of the uncertainty existing." 



(a) Salmo fario gaimardi. 



" Largest specimen observed, fifteen inches ; 



