ACANTHOPTERYGII. 109 



D. rupestris, Cuv. , a species resembling a carp, and highly 

 flavoured, is found in the fresh waters of the isles of Bourbon 

 and of Mauritius, where it is much esteemed. (l) 



Therapox, Cuv. 



Preoperculum, dentated; operculum terminating in a stout spine; a 

 strongly emarginate dorsal between the spinous and soft part: teeth 

 of the external row pointed and stronger than the rest. In some, the 

 teeth of the vomer fall out at an early period. They inhabit the 

 waters of India, and are remarkable for a natatory bladder, divided 

 into two chambers by a stricture. (2) 



It is hardly possible to separate the Datnia from them, although 

 they want the palatine teeth; their profile is more rectilinearj their 

 dorsal less emarginate.(3) 



PeLATESj 



Internal and opercular characters, the same as in Therapon; but 

 the teeth are uniformly small and crowded, and the dorsal but slightly 

 emarginate.(4) 



HeloteSj Cuv. 



Also very similar; the dorsal deeply emarginate; they are particu- 

 larly distinguished by the anterior range of teeth, which are tribo- 

 late.(5) 



Most of these fishes are marked with longitudinal blackish lines 

 on a silvery ground. 



The Percoides, with less than six branchial rays and two 

 dorsals, constitute but two genera. 



Trichodon, Steller. 



Preoperculum with strong spines, operculum terminating in a flat 

 point; no scales; mouth cleft almost vertically. But one species is 

 known, 



Tr. Stelleru Cuv.; Trachinus trichodon; Pall. Petersb. Mem. 



(1) This is the Centropome de roche, Lacep.,IV, 273. 



(2) Holocentrus servus, Bl., 238, 1, ov Sciasna jerbua, Forsk.; — JIol. 4-lineafus, 

 Bl. 238, 2; — Ther. puta, Cuv. Russel, pi. 126; — Ther. ikeraps, Cuv., Cuv. and 

 Val., Ill, liv, and the others described Vol. III. 



(2) Datnia Buchanani, or Coins datnia, Buchanan, pi. ix, f. 29, and Cuv. and 

 Val, III, Iv; — Dat. cancellata,lh., p. 144. 



(4) P elates quinque-lineatus, Cuv., et Val., Ill, 56. 



(5) Helotes Q-lineatus, Cuv., et Val., Ill, Ivii, or Esclave six lines, Quoy et 

 Gaym., Voy. de Freycin., Zool., LXX, 1. 



