FISH. 125 
Ds TEeETRAGONOPTERUS RUTILUS. Jen. 
Puatr XXIII. fig. 2. 
T’. corpore ovali, compressissimo, altitudine tertiam partem longitudinis, hdc ad basin 
Surce caudalis mensd, @quante: osse maxillari angusto, retrorsum arcuato : pinnd 
dorsali subtriangulari, paululum pone ventrales exorientt; anali levi, longa, altitudine 
retro cito decrescente ; utraque plicts membranacets, radiis longitudinaliter adheren- 
tibus, instructd: squamis in lined laterali 40, in lined inter pinnas ventrales et 
dorsalem transversa 14. 
DVO eAe 2/20; Cano rscer. Balai Vo 8 
Lone. 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. 
Cotour.—“ 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 7. 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. 
Puate XXIII. fig. 3. 
T. corpore ovalt, subelongato, valde compresso ; altitudine tertiam partem longitudinis, 
caudali exclusd, equante: osse maxillari paulo dilatato, recto: pinnd dorsali sub- 
oblonga, alta, pone ventrales exortenti; anali scabrd, altitudine retro gradatim 
decrescente ; radiis plicis membranaceis nullis: squamis in lined laterali circiter 38, 
in lined inter pinnas ventra’es et dorsalem transversd 12. 
Do 1/9) Ams 22 -0C 19s kee. Ps 13) Ves: 
Lone. unc. 3. lin. 7. 
