134 M. P. Gervais on the Freshwater Fishes of Algeria. 



possessed specimens of CoptoduSj which he has deposited in the 

 Museum. 



The Coptodon is an Acanthopterygian fish, resembling the 

 Percoids, and especially the Ruffe, in some of its peculiar cha- 

 racters ; but it is pharyngognathous, which necessitates its 

 removal into another group ; and its maxillary teeth are trench- 

 ant and notched, hke those of the Glyphisodons, which Cuvier 

 arranges in the family of the Scisenoidei. Moreover its scales 

 are destitute of those numerous little points on the free margin 

 which are observed in those called ctenoid; and thus it would be 

 a fish of the great division of the Cycloidei of Agassiz, which 

 forbids its being placed in the same genus as the Glyphisodons, 

 as was proposed by M. Valenciennes'^. The scales of Coptodus 

 have their margin of insertion festooned, an arrangement which 

 does not occur in all the Cycloidei, but is found in some of them, 

 among which I may cite the Cyprinodontes, Moreover the 

 Coptodon is not the only Acanthopterygian in which similar 

 scales may be indicated. M. Agassiz has already pointed out 

 that certain genera of that order present them ; and among these 

 he cites various Labroidei, including the Bolti of the Nile, 

 associated by Cuvier, in his genus Chromis, with several marine 

 species, which are, on the contrary, Ctenoids. The Coracin, or 

 Little Castagneau, represents in the Mediterranean the marine 

 Chromides — fishes very different from the Bolti, and which must, 

 indeed, be placed in a different genus, not only on account of 

 the form of their scales, but because their teeth are villiform 

 instead of being trenchant and incised like those of the Bolti, the 

 Coptodon, and the Glyphisodonts. Some authors even think that 

 the marine Chromides should be referred to the genus Helias, 

 estabhshed by Cuvier and associated by him with the Scisenoidei. 

 This is the opinion adopted by Charles Bonaparte in his Cata- 

 logue of the Fishes of Europe ; and I believe it may very well 

 be sustained. 



Thus the Bolti, or Chromis niloticus, which M. Peters met 

 with in Mozambique, becomes the type of a small distinct group, 

 characterized by its fluviatile habitat, its trenchant and incised 

 teeth, and its cycloid scales. In Africa (that is to say, on the 

 same continent with it) we find some analogous Fishes. 



At a short distance from the Orange River, in some small 

 lakes which are dry during the hottest season, Dr. Andrew 

 Smith discovered an Acanthopterygian very similar to the Bolti, 

 and regarded both by Peters and J. Miiller as only differing 

 from it specifically ; this is his Tilapia Sparmanni-f, The natives 

 believe that this fish buries itself in the mud like the Tortoises, 



t niustr.Zool. S. Africa, Pisces, pi, 5 (1849). 



