Cope.J "^ [Jan. 5. 



the caudal fins. The eye is also smaller thaa la the 0. affinis. The lip is 

 evea weaker than in the Hisonotus leptochilus. 



Rio Jacuhy, Rio Grande do Sul ; numerous specimens. 



Otocinclus fimbriatus sp. nov. 



Form moderately stout ; depth at base of D. I. entering length without 

 caudal fin, four times. Head rather depressed with the muzzle rounded, 

 entering the length (measured to opercular border) three and a half times. 

 Eye entering length of head 4.25 times, and the flat interorbital space 

 2.75 times. Posterior lip well developed, coarsely tubercular, its border, 

 together witli the border of the anterior lip and the inner edge of the 

 beard, fringed with obtuse processes. Occipital plate with acute apex, 

 separated from base of dorsal spine by two transverse plates and a small 

 median posterior one. Venter with three series of scuta; a lateral series 

 of long ones directed forwards on each side, and a row of median scuta 

 in contact with them. Scales everywhere hispid. Supratemporal perfo- 

 rations small, numerous, but concealed by the integument. Inferior and 

 superior aspects of caudal region flattened, and separated by an angular 

 keel from the sides. 



Origin of dorsal fin immediately above that of the ventral. Caudal 

 lobes acute, equal. Radii, D. I. 7 ; P. I. 6 ; V. I. 5 ; A. I. 5. Pectorals 

 reaching a little beyond base of ventrals ; latter barely reaching base of 

 anal. Twenty-five rows of scuta in lateral line. 



Color, light reddish yellow. There are four large dusky spots along 

 the lateral line, the anterior enlarged and obscure. A series of corre- 

 sponding dorsal spots. Caudal fin with three vertical dusky bars, which 

 are sometimes broken into spots. Other fins with a dusky spot at base ; 

 the anal and dorsal with the spinous ray entirely dusky. Below, straw 

 color. 



Total length, 38.5 mm.; length to base of caudal fin, 28 mm.; length 

 to base of anal, 18.5 mm.; length to base of ventral, 13 mm.; length to 

 base of pectoral, 7.5 mm ; interorbital width, 5.5 mm. 



This is the smallest of the Silurid?e here described, and is to be com- 

 pared with the Otocinclus affinis already mentioned. The angulation and 

 elevation of the nuchal region described bj' Stcindachner as characteristic 

 of that species are here wanting, and the fringe of the lips is not figured 

 nor described by him. The eye is considerably smaller, entering the 

 length of the head to the apex of the occipital shield 5.5 times instead of 

 four times. In the affinis there is a longitudinal lateral band instead 

 of spots, and the fins are not represented as spotted, as is the case with the 

 0. fimbriatus. As compared with the 0. flexilis, the 0. fimbriatus difTer- 

 greatly in the tubercular and fringed lip, relating to it in this respect 

 much as the Ilisonotus Icevior does to the H. leptochilus. It is a smaller 

 species than the 0. flexilis, and is more brightly colored and with less 

 numerous lateral spots. The ventral fins are relatively longer, and the 



