SALMONIM). 67 



Sahno hamatus, Cuv. Regne Anim. ; Cuv. and Val. xxf, p. 212, pi. 615. 

 Salmo gracilis, Couch, Report, Royal Cornwall Polytec. Soc. 1859 and Fish. 

 Brit. Isles, iv, p. 216, pi. ccxvi. 



Salmo argenteus, Giintlier, Catal. vi, p. 86 (not Cuv. and Val.). 



Salmon, Russell, 1864, pp. 234; Couch, Fish. Brit. Isles, iv, p. 163, pi. ccxi. 



B. xi-xii, 13-14 (&=*), P. 14, V. 9, A. 11 (|:)/0, C. 19, L. 1. 120-125, L. far. H-H 

 Vert. 59-60, Coec. pyl. 53-77. 



Body rather elongate, with the abdominal profile more curved than that of the 

 back. The proportions of one part, of the body to the remainder vary consider- 

 ably in this fish, thus in the young we find a comparatively large head and eyes, 

 a short snout and rounded body, &c, : but as the adult stage is attained there is 

 greater depth of the body due to a more prominent abdomen. After bi'eeding, the 

 kelts are recognizable by low, lanky bodies and long heads. The length of the 

 head varies with age and sex, being comparatively slightly longer in the parr than 

 in the female grilse or salmon, while in the male salmon it is longer than in the 

 female. Length of head from 4j to 4| or even 5 in the parr and male salmon to 

 5 or 5i in the female salmon and grilse, while in barren males it is similar to 

 what is seen in females, of caudal fin from 6 in the parr to 7\ in the salmon, 

 height of body, which is greatest beneath the origin of the dorsal fin, 4 to 5 in 

 the total length. Eye situated slightly in front of the middle of the length of 

 the head (or in the middle of that length in breeding males) and comparatively 

 much smaller in adult than in young fish : interorbital space convex and equal 

 to about 2/3 the length of the postorbital portion of the head. Snout much pro- 

 duced in the male, and during the breeding season the extremity of the lower 

 jaw is provided with a strongly curved prominence which precludes the closure of 

 the two jaws. The posterior extremity of the maxilla reaches to beneath the 

 middle of the eye in the parr but beyond its posterior extremity in the adult : 

 while it is comparatively wider in the young than in the adult. Opercle higher 

 than wide, from about 1/5 more in the parr, or 1/4 in the grilse or young salmon, 

 and 1/2 in large salmon : subopercle from 1/2 to 1/3 of the height of the opercle, 

 while its posterior margin forms a semi-circular curve along with that of the 

 opercle.* Preopercle with its angle rounded and having a rather distinct lower 

 limb. Teeth in a single row in the jaws and palatines, the pre- 



maxillary ones being rather stouter </ \ than those in the mandibles, while 

 the maxillary and palatine ones are still smaller. In adults the teeth 



are often found to be larger in the /. s jaws of males than in those of 

 females. Head of the vomer without (; teeth, which are mostly in a single 



row along its body, and which are gradually lost at an early age, com- 



mencing from behind forwards, so fgj that in a half-grown or adult 



salmon only 1 to 4 are present, the anterior 2 of which are occasionally 



in a double row : in the parr and smolt a double row exists along 



the body of the vomer which \. .'/ anteriorly is usually armed with 

 4 teeth placed in a single row. ^ Three to six sharp curved teeth 



on each side of the tongue. Fins Mature fish have the fins shorter and more 

 rounded than is seen in sterile ones. The rayed dorsal fin is a little longer at its 

 base than is its highest ray. Pectoral in adults as long as the head excluding the 

 snout, and does not reach half-way to the ventral, whereas in the parr it extends 

 2/3 of the distance. Ventral in adults reaches half-way to the base of the anal in 

 the parr 2/3, anal one-fourth higher than its base is long. The form of the caudal 

 alters with sexual development : in the young parr it is deeply cleft (see pi. ex, 

 f. 2) up to 2 or2| feet in length, it is as a rule truncated, while with advancing age 

 it becomes more square. Scales in the caudal portion of the body they are 

 larger in this than any other British species of the genus, there being from 11 to 12 

 rows in an oblique line running from behind the adipose dorsal fin downwards and 



* In Yarrell it is correctly observed that what distinguishes Salmo solar from all other species is 

 the form of the opercular bones, which show a rounded outline to the posterior edge of the gill-covers, 

 the longest diameter of which to the nose would be in a line through the eye, while in all othor 

 British migratory species the same line would pass below the eve. 



5* 



