42 ZOOLOGY OF THE VOYAGE OF THE BEAGLE. 



sented in the ' Histoire des Poissons/ and of which there are evident traces, though apparently 

 much effaced by the action of the spirit. 



Habitat, Maldonado Bay, Rio Plata. 



This species, which Cuvier and Valenciennes consider as the Guatucnpa of 

 Margrave, was obtained by Mr. Darwin at Maldonado. M. D'Orbigny had 

 previously taken it at Monte Video. The only respects in which Mr. Darwin's 

 specimen differs from D'Orbigny's, is in its having two more rays in the soft 

 dorsal, and a slightly longer anal spine, judging from the figure in the ' Histoire 

 des Poissons;' but I cannot imagine that they are distinct on these grounds 

 only, so exactly do they agree in all their other characters. 



CORVINA ADTJSTA. Agassiz. 



Corvina adusta, Spix et Ac/ass. Pisces Brazil, p. 12G. tab. 70. 



Form. — Greatest depth beneath the commencement of the first dorsal fin, and equalling one- 

 fourth of the entire length. Back somewhat carinated, and moderately arched, forming one 

 continuous curve with the profile, which falls with considerable obliquity. Ventral line nearly 

 straight, and the abdomen much flattened in front of, and between the ventrals. Len° th of the 

 head just equalling the depth of the body. Snout obtuse, with two small lobes at bottom, one 

 on each side of the extremity, as in several other species of this genus. Mouth horizontal, at 

 the bottom of the snout ; when closed, the maxillary reaching a little beyond a vertical from 

 the anterior margin of the orbit. Four pores beneath the symphysis ; and seven, in two rows, 

 round the extremity of the snout; those in the lower row large. Jaws nearly equal ; the upper 

 one perhaps a little the longest. Teeth forming a velutine band above and below ; those above 

 with an outer row of somewhat longer and stronger ones. Eyes rather small ; their diameter 

 about one-fifth the length of the head. Nostrils consisting of two round apertures in advance 

 of the eye, the posterior one largest ; the anterior with a raised margin. Preopercle a little less 

 than rectangular, with the angle at bottom somewhat rounded : the ascending margin 

 rectilineal, sloping rather in advance of a vertical, and distinctly toothed, the teeth becoming 

 smaller upwards : at the angle are two stronger teeth or spines, the uppermost directed back- 

 wards and a little downwards, the lowermost downwards and a little backwards ; between 

 these two teeth there is an interval; the basal margin of the preopercle is quite smooth. 

 Opercle terminating in two flat inconspicuous points. 



Snout, cheeks, and gill covers, covered with scales of very unequal sizes: those serving as a 

 boundary between the cheek and the preopercle, also a row above each orbit, a few at the 

 upper angle of the opercle, some on the suprascapular lamina, and a row extending thence 

 upwards and forwards to the occiput, much smaller than the others. Scales on the body of 

 moderate size, arranged in oblique rows; about fifty-five in a longitudinal line, and nineteen or 

 twenty in a vertical. One taken from above the lateral line, and nearly in the middle of the 

 length, is oblong, approaching to circular, its surface marked with a number of concentric, 



