SYNOPSIS OF BRITISH GENERA. 



Synopsis of British Genera. 



1. Salmo. — Maxillai'y long : dentition strong and complote. Scales small. 

 Anal rays in moderate numbers (IJj or less). Pyloric appendages numerous. 



2. Thi/mallus. — Maxillary short : small teeth in the jaws, vomer, and on the 

 palatine bones. Anterior dorsal fin many rayed. Scales of moderate size. 

 Pyloric appendages numerous. 



3. Coregonus. — Maxillary short : teeth if present minulc. Anterior dorsal fin 

 with few rays. Scales of moderate size. Pyloric appendages numerous. 



4. Osmerus. — Maxillary long : dentition complete, with fang-like teeth on the 

 vomer and tongue. Scales of medium size. Pyloric appendages few. 



5. Arfjentina. — Maxillary short : teeth absent from jaws. Anterior dorsal fin 

 with few rays. Scales rather largo. Pyloric appendages few or in moderate 

 numbers. 



Of the foregoing my remarks will be restricted to species belonging to the two 

 first genera, or those of Salmo and Thymallus, forms in which their eggs are 

 much heavier than the water, and are mostly deposited beneath sand or 

 gravel. 



The blood discs of the fishes of this family are of very large size, those of 

 the salmon being nearly equal to such as are found in the cartilaginous sturgeon. 

 Gulliver (Proc. Zool. Soc. 1872, p. 834) recorded the average diameter of the 

 red corpuscles of the blood in the following species — L. D. signifying the "long 

 diameter" and S. D. "short diameter " : — ;SaZ»io salar, L. D. -j-sViT) S. d. -^^Vo- ^^ 

 fario, L. D. y/aT, s. B. a-g^o- ^' ferox, L. D. xs-Vt) ^- ^- -2 9Vo- S. foiiUnaUs, L. D. 

 ttVsj S- r>. aaVe- Thymallus vulgaris, L. D. y-eV*) S- ^- 2-oVo- These corpuscles 

 appear to be at least a third larger than the corresponding corpuscles of most 

 other osseous fish. 



Genus I. — Salmo, Artedi. 

 Fario and Salar, Cuvier : Trutta and Salvelini, Nilsson. 



Branchiostegals from nine to tliirteen : pseudobranchice present. Eyes lateral. 

 Cleft of mouth deep, the posterior extremity of the upper jaio reaching to beneath the 

 hind edge of the eye or even beyond. Teeth conical, pirescnt on the jaws, vomer, 

 palatine bones and tongue, absent from the pterygoids. Anterior dorsal fin with a 

 moderate number of rays (10-15) : anal with rather few (10-13). Scales small and 

 cycloid. Lateral-line straight. Ccecal appendages mimerous. A pancreas present. 



Geographical distribution. — These physostomatous fishes, found in the fresh 

 and salt waters of Europe, Asia, and America, are most abundant in the Arctic or 

 colder regions, in contradistinction to the distribution of the carps and siluroids, 

 which augment in numbers the nearer we approach the tropics. Temperature 

 would appear to limit the distribution of these fishes to the colder and temperate 

 regions, or we should find them extended to the Mediterranean, where Davy 

 remarked he had only known a stray salmon captured off the coast of Malta.* 



The indigenous species belonging to this genus have been divided into (1) 

 Salmones, or true salmons, wherein the body and the head of the vomer are 

 toothed at some period of their lives, and (2) the Salvelini or chars, wherein the 

 vomerine teeth are restricted to the head of that bone. 



* Davy (Physiological Ecsearches, 1863, page 82) gave the result of some investigations that 

 he had made on the temperature of salmon captured with an artificial fly. 



Sept. 1862 — Temper, of river, 56° : of male salmon, under liver, opened immediately, 59°: in the 

 heart still pulsating, 58°. 

 Sept. 1862 — Temper, of river, 58° : of salmon, under liver, opened immediately, 60° 



,, ,, 58°: of grilse ,, ,, 5'J-5. 



In all these three instances the thermometer was introduced into the wound made by the gaff in 

 the thick muscles of the back from which blood was exuding. 



