CHAPTER IX. 



FRESH- WATER FISHES OP THE ORDER PHYSOSTOMI (continued}. 



FAMILY SALMONID^E (concluded) : SUB-GENUS CHARR : Salmo salvelinus S. umbla S. 

 alpinus S. nivalis S. killinensis S. perisii S. colii S. willughbii S. rutilus S. carbon - 

 arius S. grayi S. hucho S. losses GENUS LUCIOTKUTTA : L. leucichthys GENUS OSMERUS : 

 Smelt GENUS COREGONUS : Species with the upper jaw prolonged Species with the snout 

 obliquely truncated Species with the snout vertically truncated Powan Species with the 

 mandible longer than the snout Pollan Vendace GENUS THYMALLUS : Grayling Thymal- 

 lus microlepis. 



SUB-GENUS : Salvelini, or Charr. 



THE Salvelini is a group or sub-genus of the Salmon tribe, popularly 

 known as Charr, and widely distribiited in Europe, Northern Asia, and North 

 America. The species of Charr are united tog-ether, because their vomerine 

 teeth are limited to the head of the vomer. This character, insignificant enough 

 in itself, is useful in facilitating the study of a large tribe of variable fishes 

 which require classification. The members of this group, like Trout, vary with 

 almost every sheet of water, so that local races and varieties have been de- 

 veloped, which many writers term species. These mutations of form do 

 not confuse our conception of a species ; because they demonstrate a gradual 

 modification of characters, with varied geographical distribution, which 

 enables us to recognise the steps by which circumstances of existence have 

 changed structures which, if examined in one locality only, seem to be stable. 



We would greatly reduce the number of species of Charr, although they 

 are founded on characters which in other groups might characterise fishes well ; 

 but the variability of specific character in almost every one of the species 

 adopted in the British Museum Catalogue favours their union into larger 

 species, such as were in favour with Louis Agassiz, Yarrell, and the earlier 

 naturalists. Thus we find the number of fin-rays presenting but little 

 difference in a large number of so-called species of Charr. The number of 

 vertebra is almost as constant. The colouring is on the same general plan in 

 them all. And even the pyloric appendages in the majority of these fishes 

 vary in number between small limits. 



The number of scales in the lateral line, however, is one of the most 

 variable characters in the geographical races, and we are disposed to asso- 

 ciate Salmo salvelinus, S. ^lmbla, S.alpinus,S. nivalis, S. killinensis, S. perisii, 

 S. willughbii, and S. colii as types of Salmo salvelinus, in which the variation 



