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



In describing his Haligenes Tristrami, Dr. GUnther ?ias called 

 the attention of naturalists to a fish, of the Mediterranean region 

 of Africa, with regard to which science still possesses but few 

 details, namely the Sparus Desfontainii of Lacepede*, which 

 Cuvier and Valenciennes have placed among the Chromides 

 under the name of Chromis Desfontainii. It would be the more 

 interesting to know what relations this supposed Sparus or 

 Chromis may have with the Bolti, as, like the latter, it is not 

 found in the sea. Lacepede tells us that it was discovered by 

 the celebrated botanist whose name it bears in the hot waters 

 ( + 30° R.) of the town of Cafsa in Tunisia ; this water is po- 

 table when allowed to cool. Lacepede adds that Desfontaines 

 also met with fishes of this species in the rivulets of cold and 

 brackish water which irrigate the date- plantations at Tozzer, 

 likewise in the district of Tunis. Under the name of Chromis 

 Desfontainii the museum possesses some fishes which come 

 precisely from the thermal waters of Cafsa; and M. Dumeiil, 

 with his usual complaisance, has been kind enough to afibrd me 

 facilities for examining them, as well as many other rare species 

 which I required to study in order to confirm the conclusions 

 of this investigation. * 



Sparus Desfontainii is neither a Sparus nor a Tilapia, that is 

 to say, a C bromide of the same genus as the Bolti. In fact, 

 although it has the jaws furnished with teeth of nearly the same 

 form as in the latter, which distinguishes it frotn the Spari^ it 

 is clearly separated from the Bolti by the ctenoid form of most 

 of its scales, and in this respect presents the ordinary condition 

 of the Acanthopterygii. It teeth and its scaling, therefore, ap- 

 proximate it more to Glyphisodon than to any other genus ; and 

 it is with the Pharyngognathi of this genus that it must be 

 classed, unless we prefer to regard it, especially on account of 

 its habitat, as forming a separate genus ; for the Glyphisodons 

 are marine fishes. I do not, however, consider myself autho- 

 rized, by the comparisons which I have hitherto been able to 

 make, to separate Sparus Desfontainii from Glyphisodon ; and I 

 do not doubt that M. Valenciennts, who wished to make the 

 Coptodon a species of this genus t, notwithstanding its cycloid 

 scales, would have expressed the same opinion with regard to 

 the fish from Cafsa. 



Independent of the data which it may furnish for the nomen- 

 clature of ichthyology, this little discussion leads us to the 

 remark, certainly worthy of being brought forward, that the 

 continental waters of the Mediterranean region of Africa contain 

 a fish evidently nearly allied by its principal characters to the 



* Histoire des Poissons, iv. pp. 161 & 162. 

 t Glyphisodon Zillii, Valenciennes, loc. cit. 



