FISH. 127 



Colour.— Much as in the T. 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. 



Plate XXIII. fig. 4. 

 T. corpore ovali, valde compresso: altitudine terliam partem longitudinis totius 

 (Equante : ore parvo ; osse maxillari brevissimo, dilatato, margine poster iore recto : 

 dentibus minutis, multicuspidatis : dorsali subtriangulari, pone ventrales exorienti ; 

 anali (in uno sexu ?) scabrd, altitudine retro subito decrescente ; his pinnis plicis 

 membranaceis nullis : squamis in lined longitudinali 35, in lined inter pinnas 

 ventrales et dorsalem transversa 10 : lined later ali interruptd, hand Jinem pinnce 

 pectoralis attingente. 



D. 1/10 ; A. 2/18 ; C. 18, &c ; P. 1 1 ; V. 7 

 Long. unc. 2. lin. 8. 

 Form.— Oval, and not very dissimilar in general form to the T. 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 stria on the basal portion, and conse- 

 quently no fan ; but they are very regularly marked with the usual finer stria? 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 



