ME. F. DAT OK BRITISH SALMONES. 409 



single row along the body of' that bone ; caudal fin with pointed 

 lobes. B.ferox: D. 13, A. 10-11 ; no teeth on the head of the 

 vomer, but a double row along the body of the bone ; caudal fin 

 truncated*. 



The example of the " hog-backed trout " (which I exhibit) has 

 D. 14, teeth on the head of the vomer, and a distinct lower limb 

 to the preopercle, thus belonging to /S. nigripinnis. Likewise 



A . 11, a double line of teeth along the body of the vomer, and the 

 caudal fin truncated, which is given as diagnostic oi B.ferox. 



I have likewise six smaller examples of S. nigripinnis in which 

 teeth are present on the head of the vomer and in a zigzag line 

 along the body of that bone ; the caudal fin in the smallest has 

 pointed lobes, which have become rounded in larger specimens ; 

 the capcal appendages varied from 35 to 44. In some of these 

 fish the posterior margin of the preopercle was rounded, and had 

 no distinct lower limb. The maxilla was much feebler than seen 

 in some other local races of brook-trout, which was remarkably 

 the case on comparing it with a beautiful Yorkshire variety sent 

 me by Mr. G. Brooks, F.L.S. ; but among these Yorkshire spe- 

 cimens I found great differences to exist, 



I now determined to go to Cornwall and ascertain whether the 



B. cornubiensis really differed from a young S, nigripinnis ; and 

 the first thing I ascertained at Penzance was, that the little brook- 

 form, if placed in large pieces of water, attained to several pounds 

 in weight. I obtained a considerable number which externally 

 only differed from 8. nigripinnis in colour, the parr-marks of the 

 young stage being continued throughout life in these small trout 

 takeu from the streams, The brook-trout from the Cotteswolds 

 has as weak a maxilla as the S. nigripinnis, although it is clearly 

 a typically-coloured S.fario. 



Sahno orcadensis, Giinther, 1865. — In the ' Catalogue of the 

 Pishes in the British Museum,' vi. p. 91, it is observed that 

 " Sir J. Eichardson mentions this trout in the Fauna Bor.-Amer. 

 Pish. p. 142, referring it to the ' Frith-trout;' but this appears 

 to have the maxillaries feebler and the scales smaller." In 

 examining this question, we undoubtedly find that in the third 

 edition of Yarrell's ' British Fishes,' edited by Sir J, Eichardson, 

 allusion is made to the Loch-Stennes trout under the head of the 



* " The caudal fin (in Salmonoids) especially undergoes considerable changes 

 with age, and dependentlj' upon the sexual development. Young specimens of 

 all species have this fin more or less deeply excised." (Giinther, Cat. vi. j). 5.) 



LINN. JOUKN. — ZOOLOGY, VOL. XVI, 30 



