44 ZOOLOGY OF THE VOYAGE OF THE BEAGLE. 



1. Umbrina arenata. Ciw. et Val. 



Umbrina arenata, Cuv.et Val. Hist, des Poiss. torn. v. p. 141. 

 Form.— Rather elongated, with the back very little arched ; the greatest depth contained about five 

 times and a quarter in the entire length. Length of the head about equal to the depth of the 

 body. Profile falling very gradually, and nearly in a straight line, in front of the dorsal. 

 Snout very much projecting j the margin at bottom, above the upper jaw, divided into four 

 lobes which are cut square at their extremities. Round the end of the snout, and immediately 

 above the lobes, is a double row of pores, the lower ones large. Also four pores beneath the 

 symphysis of the lower jaw. Barbule at the chin scarcely exceeding a line or a line and a half 

 in length. A band of velutine teeth in each jaw, with an outer row in card ; these last 

 moderately strong, sharp, and rather wide apart, not above fourteen or sixteen in the row. 

 Preopercle very obsoletely denticulated. Opercle with two flat points not much developed. 



First dorsal triangular ; the first spine very small ; the second, third and fourth elevated 

 rather in a point, the third equalling two-thirds of the depth of the body or more. Second 

 dorsal nearly twice the length of the first. Anal commencing opposite the sixth soft ray of 

 that fin, short, and terminating considerably before it; the anal spine weak, and very little 

 more than half the length of the soft rays. Caudal with the posterior margin sinuous, the 

 upper part being slightly crescent-shaped, the lower portion rounded, and broader than the 

 upper. Pectorals a very little shorter than the head. Ventrals attached a little behind the 

 pectorals, and not passing beyond them. In the axilla of the pectorals is a small triangular 

 membranous lamina : there is also a narrow pointed one in the axilla of the ventrals covered 

 with scales. The scales on the body are thin, rather small, somewhat rhomboidal, with their 

 free margins ciliated, and with a fan of twelve stria? behind. 



B. 7 ; D. 10—1/25 ; A. 1/8 ; C. 17 ; P. 21 ; V. J/5. 



Length 9 inches 6 lines. 



Colour. — " Body mottled with silver and green: dorsal and caudal fins lead-colour." — D. 

 In spirits, the colour appears dusky brown, with darker mottlings and silvery reflections ; paler 

 beneath. The fins are dusky, but the basal half of the dorsal is darker than the upper. The 

 pectorals are darker than the other fins, especially the inside; on the left pectoral, the dark 

 colour is restricted to three broad transverse fascia?. There are also on the pectorals and anal, 

 and on most of the scales on the body, small blackish dots, as mentioned in the ' Histoire des 

 Poissons.' 



A second specimen, smaller than the above, has the back rather more arched, the greatest depth 

 being only five times in the length. The outer row of teeth in the upper jaw is not quite so 

 conspicuous, the teeth being smaller and closer-set, and consequently more numerous. The 

 soft dorsal and anal have fewer rays. 



D. 10—1/22; A. 1/7; &c. 



Length 7 inches 3 lines. 



In all other respects similar to the specimen first described. 



Habitat, Bahia Blanca, and Maldonado. 



