M. P. Gcrvais on the Freshwater Fishes of Algeria, 135 



and thus waits until the excavations in the soil in which it 

 remains during the dry season are inundated afresh. Dr. Smith 

 was unable to verify this statement. 



Other fishes having the form of the Bolti live in the Gaboon 

 and in the Senegal. M. A. Dumeril"^ has described nine species 

 of them as distinct, calling them Tilapia, this name being 

 adopted by him as that of the genus of which the Bolti is the 

 oldest known form. 



It is also in the same division that must be placed Haligenes 

 Tristrami, Giintherf, taken, like M. Zill's Coptodons, at Tug- 

 gurth. Between this fish and the Bolti, or Coptodon, the only 

 difi'erence that I can see is that of the pharyngeal teeth, indi- 

 cated as cardiform in the specimen brought by Mr. Tristram, 

 which cannot be applied to tliese teeth taken singly in the Bolti, 

 but becomes conformable to the reality if the author intended, 

 as I suppose, to speak of the bone supporting these teeth. 



M. Peters was the first to demonstrate the resemblance which 

 exists between the Bolti, Tilapia^ and Coptodon. Having lately 

 had the opportunity of comparing the Bolti of the Nile with the 

 Coptodon from Tuggurth sent me by M. Zill, I have been able 

 to judge of the correctness of this approximation indicated to 

 me by the learned naturalist of Berlin, and to assure myself 

 that these fishes are certainly of the same species. The simi- 

 larity of their characters is complete; there is nothing, even to 

 their pharyngeal teeth, both superior and inferior, that does not 

 present tlie same details of form and arrangement. In both 

 cases we find the same distribution of these teeth, the same 

 inequalities in their size, their villiform appearance, and in some 

 the division of the apex into two or three small, short, unequal 

 points, slightly recurved, and arranged in a linear series. A 

 certain number of them also have the apex tinged with red, 

 nearly of the same shade as the teeth of some Shrews. 



There can be no doubt that the Acanthopterygian with 

 cycloid scales which is found in certain springs, both fresh and 

 salt, of the Algerian Sahara, and which, in several places, has 

 been seen issuing with the waters of these springs, or those of 

 artesian wells, in the same way as the Cyprinodons already 

 mentioned, is the same fish as the Bolti of the Nile; it enters, 

 therefore, with this into the genus Tilapia. The Tilapia Spar- 

 manni is itself a Bolti ; and it is not certain that the analogous 

 fishes which have been indicated in the Gaboon and Senegal 

 under other names are all specifically distinct from it. In any 

 case they must be associated with it geuerically, as also appa- 

 rently must Haligenes Tristrami. 



* Archives du Museum, tome x. p. 2ol. 



t Proc. Zool. Soc. London, 1859, p. 461, pi 9. fig. B. 



