INTRODUCTORY ig 



and particularly those of the genus Salmo : — 



"A double or zigzag series of teeth along shaft of vomer, 

 sometimes deciduous in the adult." 



It is interesting to note in passing that from a study of their skeletons, 



and in particular their skulls, Mr. Regan finds that no doubt is left that 



the Pacific species of salmon and trout " form a perfectly natural group 



that differs in several characters from the Salmon and Trout of the 



Atlantic." 



In restricting himself in his book, however, to the British members 



of the family SalmonidcE, Mr. Regan again distinguishes four, but a 



different four, genera, namely: (i) Salmo (Salmon and Trout), (2) 



Salvelinus (Char), (3) Coregonus (Whitefish), and (4) Thymallus 



(Grayling), a fact which reminds one of the morphologist's caution in 



viewing systems of classification, and the special features of Salmo and 



Salvelinus are given thus : — 



" Mouth rather large, the maxillary extending at least to below 



the middle of the eye; teeth well developed; scales small or 



moderate; dorsal fin with 10 to 16 rays"; 

 and particularly those of the genus Salmo : — 



" No depression behind the head of the vomer, and a double 



or zigzag series of teeth present on the shaft of that bone, at least 



in the young." 



It only remains to complete this classification by noting that the genus 



Salmo embraces two species, and two species only, namely, (i) Salmo 



salar, which is, of course, the salmon ; and (2) Salmo trutta, which is the 



trout — be that what it may, sea-trout or trout, one or other, or both. 



Thus we arrive at the basis of the theory that there is only one species 



of trout in these islands. 

 IIP 



Except in so far as many, up to this point, may, like myself, have 



been treading on somewhat unfamiliar ground, I see no room for 



criticism, and we have certainly arrived at a bare systematic conception. 



if not of the fish itself, at least of the limits within which further 



particulars may be sought for, and these we may now proceed to seek. 



