28 SALMONID^, 



in several characters, it appears to me to be much more probable 

 that they are hybrids between the Sea-Trout and the common 

 River-Trout. 



Yarrell's- collection of these fishes was chiefly composed of English 

 and, Welsh specimens, and he promiscuously named a part S. trutta 

 and another S. eriox, generally applying the former name to females 

 (with a shorter head), and the latter to males (which have the head 

 more elongate). However, he was perfectly right in directing atten- 

 tion to the difference in the shape of the gUl-cover, which is very 

 characteristic for the two species, at least in most of the individuals. 

 But he was not aware that numerous variations occur, and that there 

 are specimens of 8. trutta and S. eriox {camhrims) which have the 

 gUl- covers of precisely the same shape. 



In these cases only an examination of the internal parts of the 

 maxillary and mandible can decide to what species such individuals 

 ought to be referred, these bones being much stronger and more solid 

 in S. cambricus than in S. trutta. It is probable that the figure of S. 

 trutta given by YarreU on the first page of the description is taken 

 from a Scotch example which he procured in the " London market" 

 for his collection. 



iS'ilsson's description agrees very weU with the British Salmo 

 trutta, except in one point, viz, in the length of the maxillary bone, 

 which, according to him, extends to behind the eye. This is the 

 case in very old males only. 



Description of a Male Sea-Trout from the Tweed, cau(jht in the month 

 of November, apparenthj engaged in spawnim/. 



inches. 



Totallength 35 



Greatest depth of the body 7f 



Length c f the head 8 



Least depth of the taU 3 



Distance between end of snout and eye 3^ 



Diameter of the eye ^ 



Length of the maxillarj' bone 3^ 



Greatest width of opercidum 1^ 



Greatest depth of opercidum 2| 



Distance between occiput and dorsal fin 11 



Distance between end of dorsal and root of caudal . . 12 



Length of base of dorsal 3 



Length of pectoral 4A 



Distance between root of pectoral and root of ventral 9^ 



Length of ventral fin 3^ 



Distance between root of ventral and origin of anal 7 



Length of anal 2^ 



Length of longest caudal ray 4 



Length of middle caudal ray . . . , 2^ 



The great development of the jaw-bones, and of the hook of the 



