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Show 42 ZOOLOGY OF TilE VOYAGE OF TilE 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 Guatucupa of Margrave, was obtained by Mr. Darwin at Maldonado. M. D'Orbigny had previously taken it at Moote Video. The only respects in which Mr. Darwin's specimen differs from D'01·bigny'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 t.heir other characters. ConviNA ADUSTA. Agassiz. Corvina adusta, Spix et .A[JasS. Pisces Brazil. p. 126. tab. 70. FonM.-Greatest depth beneath the commencement of the first dorsal fin, and equalling onefourth of the entire length. Back somewhat carinated, and moderately arched, fot·ming 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. Length 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 vel utine 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 backwards and a little downwards, the lowermost downwards and a little backwat·ds; 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 numbet· of concentric, FISII. 43 much crowded, curved lines, somewhat undulating behind, with a fan of about twelve deeper strire converging to a point considerably in advance of the centre of the scale; the free portion is also marked with several well-marked nearly parallel lines which terminate in denticles at the anterior margin. Those on the lateral line have the mucous tubes somewhat ramified, and arc accompanied throughout its course by some minuter scales, similar to those on the head above pointed out. The lateral line is at one-third of the depth, till it arrives beneath the middle of the soft dorsal, where it falls to one-half. First dorsal of a triangular form, separated from the soft portion by a deep notch; the first spine very small and inconspicuous; the second somewhat shorter than the third ; fourth longest, nearly equalling half the depth; all the spines in this fin rather slender. The second dorsal commences with a spine somewhat longer than the last spine in the first dorsal, and not quite half the length of the first soft ray; soft rays nearly even throughout, and not equalling the highest point of the first dorsal. Anal short and somewhat rounded, commencing beneath the middle of the second dorsal, and double the height of that fin; its first spine very short and inconspicuous; second long and moderately stout, but shorter than the first soft ray by onethird; second soft ray the longest; third and succeeding ones gradually decreasing. Pectorals narrow and pointed, shorter than the head; first ray simple, the rest branched; third, fourth and fifth longest. Ventrals attached a trifle backwarder than the pectorals, which they do not equal in length; the spine much slenderer than that of the anal, and rather more than half the length of the first soft ray. Caudal squarish, but with the margin a little sinuous. B. 7; D. 10-lf28; A. 2/8; C. 17; P. 17; V. 1/5. Length 8 inches 6 lines. Cotoun.-" Above inclining to coppery, with irregular transverse baTs of brown; beautifully iridescent with violet."-D. The bars alluded to by Mr. Darwin are some dark lines which, commencing at the upper part of the back, pass forwards and downwards in an oblique direction; they bend more and more downwards as they advance, and disappear a little below the middle. The whole fish has a metallic gloss, particularly about the cheeks and gill-covers, and very visible even in its present state. A second specimen, exactly similar to the above, is nearly twelve inches in length. Habitat, Maldonado and Monte Video. I entertain no doubt of this species being the 0. adusta of Agassiz, figured in Spix's Fishes of Brazil. It is not described by Cuvier and Valenciennes, but belongs to their second section of the genus, characterized by the small spines on the ascending margin, and especially at the angle, of the preopercle. It seems to he particularly distinguished by the small scales on some parts of the head, and along the lateral line whe1·e they accompany the larger ones. These characters have not been overlooked by Agassiz. There are two specimens in the collection, the larger one taken at Monte Video, the smaller at Maltlonado. |