FISH. 



125 



2. Tetragonopterus rutilus. Jen. 



Plate XXIII. fig. 2. 

 T. corpore ovali, compressissimo, altitudine tertiam partem longiludinis, hdc ad basin 

 furcce caudalis mensd, cequante : osse maxillari angusto, retrorsum arcuato : pinna 

 dorsali suUriangulari, paululumpone ventrales exorienti; anali lesvi, longd, altitudine 

 retro cito decrescente ; utrdque plicis membranaceis, radiis longitudinaliter adhceren- 

 tibus, instructd : squamis in lined laterali 40, in lined inter pinnas ventrales et 

 dorsalem transversa 14. 



D. 1/9 ; A. 2/27 ; C. 19, &c. ; P. 14 ; V. 8. 

 Long. unc. 4. lin. 3. 

 Form.— More oval than rhomboidal: the back and nape not so much elevated as in the last species; 

 the profile falling less obliquely. Depth one-third of the entire length, measured to the base 

 of the caudal fork: head one-fifth of the same. Not above fourteen scales in the depth, and 

 forty in the lateral line, which occupies the eighth row from the top. The scales on the whole 

 similar, but with the basal margin not so straight and regular, and somewhat projecting in the 

 middle in the form of a blunt salient angle. The dorsal commences a trifle nearer the caudal, 

 and at the middle of the entire length, the caudal alone excluded. The pectorals reach just to 

 the insertion of the ventrals, which last are a trifle in advance of the dorsal. The second anal 

 spine is longer, and nearly half the length of the soft rays which follow. 

 Colour.— "Back iridescent greenish brown: a silver band on the side. Fins dirty orange: tail 

 with a central black band; above and below the band bright red and orange."— D.— The 

 colours appear very similar to those of the last species. The humeral spot, however, is less 

 obvious, while, on the other hand, the silver band on the side can still be distinguished. 



Habitat, Rio Parana, South America. 



Taken with the last species, to which it is very closely allied. Mr. Darwin 

 observes in his notes, that both are among the commonest of the river fry in the 

 Rio Parana. 



Both this and the T Abramis are distinguished by having narrow longi- 

 tudinal folds of skin attached to the basal half of the rays of the dorsal and anal 

 fins, a character which does not shew itself in any of the three species next to be 

 described. 



3. Tetragonopterus scabripinnis. Jen. 



Plate XXIII. fig. 3. 

 T. corpore ovali, subelongato, valde compresso ; altitudine tertiam partem longitudinis, 

 caudali exclusd, cequante : osse maxillari paulo dilatato, recto : pinna dorsali sub- 

 oblongd, altd, pone ventrales exorienti; anali scabrd, altitudine retrd gradatim 

 decrescente ; radiis plicis membranaceis nullis : squamis in lined laterali circiter 38, 

 in lined inter pinnas ventra'es et dorsalem transversa 12. 



D. 1/9 ; A. 3/22 ; C. 19, &c. ; P. 13 ; V. 8. 

 Long. unc. 3. lin. 7. 



