THE SALMON, THE TROUT, AND THE SHAD. 739 



2. The Salmo hamatus has invariably only one tooth on the front plate 

 of the vomer, while the Salmo salar has several teeth. 1 



3. The Salmo hamatus has a reddish-gray back, the color becoming more 

 lively on the lower portions of the sides ; the color of the belly is a 

 dull white. The Salmo salar, on the other hand, is slate-colored on the 

 back, of a subdued silver-color on the sides, and of a silvery-white, 

 shining like mother of pearl, on the belly. 2 



4. The flesh of the Salmo hamatus has much less color and is drier 

 than that of the Salmo salar. 3 



5. The Salmo hamatus has at the end of the lower jaw a protuberance, 

 (" tuuercule") which, when the mouth is closed, fits exactly into a con- 

 siderable concavity (" enfoncement considerable'''') of the upper jaw. 4 The 

 lower jaw thus forms a projecting hook, so that the upper and lower 

 jaws cannot be pressed against each other. The Salmo salar does not 

 have this hook. 



With regard to the above assertions, the following remarks are to be 

 made: 



To 1 : The number of pyloric cceca in one and the same species of sal- 

 mons varies greatly. 5 



Valenciennes found in the Salmo salar GO and in the Salmo hamatus 07 

 appendices pyloricce. In the enumerations which I have made, I was led 

 to the result that in the salmonoids which Valenciennes differentiated as 

 two species, the number of cceca is no safe distinctive character, as it 

 varied from 5G to 72, and was frequently larger in those which had no 

 hook than in the so-called "hook-salmon." Giinther states that the 

 number of cceca varies from 53 to 77 ; Richardson^ from G3 to 08. Kner 7 

 has also shown that the number of cceca in one and the same species of 

 salmonoids is extremely varying. 



To 2: The arrangement of the teeth on the vomer has been errone- 

 ously described by Valenciennes, as has been shown by Siebold. 8 Tlie 

 short front plate (chevron) of the vomer of the Salmo salar (and the S. 

 hamatus) is invariably toothless, and only the long point of the vomer 

 has teeth. But, as the fish grows older, these teeth fall out gradually, 

 and no new ones take their place, so that an entirely toothless vomer 

 is frequently found in old fish. It is evident from this — as I also 

 found in my investigations — that the number of vomerine teeth differs 

 very much. In our Bonn Museum, there are two old specimens, labeled 



1 Valenciennes, op. cit., pp. 172 and 213. 



2 Valenciennes, op. cit., pp. 174 and 217. 



3 Valenciennes, op. cit., p. 222. 

 * Valenciennes, op. cit., p. 215. 

 6 Siebold, op. cit., p. 314. 



6 Giinther, op. cit., p. 13. 



7 B. Kner, Uber die Verschiedeuheiten der Blinddiirme bei den Salmonen (in "Sitz- < 

 ungsbericbte der mathem.-naturw. Classe der kaiserl. Akademie der Wissenscbaften," 

 vol. viii, 1852, p. 201). 



8 Siebold, op. cit., p. 301. 



