FISH. 127 
Corour.—Much as in the 7. scabripinnis. The same silver band, only more brilliant; also the 
same humeral spot, and the spot at the base of the caudal extending along the middle rays. 
Habitat, Rio de Janeiro. 
The above description is that of two small specimens, similar to each other, 
obtained by Mr. Darwin in a running brook at Socego, in the province of Rio de 
Janeiro. They are probably not full grown ; but so evidently distinct from either 
of the last two species, the characters of which are in some measure combined in 
them, that I have not hesitated to give them a separate place. The silver band is 
more or less obvious in all the species of this genus brought home by Mr. Darwin, 
but it is much brighter in this than in any of the others. 
5. TETRAGONOPTERUS INTERRUPTUS. Jen. 
Puate XXIII. fig. 4. 
T.. corpore ovali, valde compresso: altitudine tertiam partem longitudinis totius 
@quante: ore parvo ; osse maxillart brevissimo, dilatato, margine postervore recto : 
dentibus minutis, multicuspidatis : dorsali subtriangulart, pone ventrales exoriente ; 
anali (in uno sexu?) scabrd, altitudine retro subito decrescente; his pinnis plicis 
membranaceis nullis: squamis in lined longitudinal 35, im lined inter pinnas 
ventrales et dorsalem transversd 10: lined laterali interruptd, haud finem pinne 
pectoralis attingente. 
D. 1/10; A. 2/18; C. 18, &&€; P.11; V.7 
Lona. unc. 2. lin. 8. 
Form.—Oval, and not very dissimilar in general form to the 7’. rutilus, but rather more elevated 
above the shoulder. Depth exactly one-third of the entire length: head one-fourth of the 
same, caudal excluded. Profile not exactly straight, but very slightly hollowed out at the 
crown, then as slightly protuberant above the eyes, whence it falls more rapidly in front, giving 
the snout a short and blunt appearance. Mouth much smaller than in any of the preceding 
species, owing to the extreme shortness of the maxillary, which is broad, with the anterior mar- 
gin curving outwards, but the posterior one straight. Teeth very small; the points on the 
cutting edges numerous (five or six on each tooth) and nearly equal; apparently only one row 
on the intermaxillary, and the same in the lower jaw; none on the maxillary. Eyes and nos- 
trils as in the other species, but the anterior orifice of the latter larger. Subopercle much 
larger, forming a greater portion of the gill-flap. Scales relatively larger; only ten in the 
depth, and thirty-five in the length. They have no deep strie on the basal portion, and eonse- 
quently no fan; but they are very regularly marked with the usual finer striz concentrically 
arranged, except on the free portion where they become indistinct. 
The lateral line occupies the sixth row of scales from the top, but is very soon interrupted, 
coming to an end before it has reached the length of the pectoral, and not carried over more 
than eight or nine scales in the length. Dorsal subtriangular, commencing exactly at the 
middle of the length, caudal excluded. Anal shorter than in the other species, and not reach- 
ing so near the caudal; two spines, but the first extremely minute. Caudal forked for half its 
