OCR Text |
Show 44 ZOOLOGY OF TilE VOYAGE OF TilE BEAGLE. 1. UMBRINA ARENATA. Cuv. et Val. Umbrinn. arcnata, Cuv. et Val. Ilist. des Poiss. tom. v. p. 141. Fomr.-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, ~n fron~ .of th.e dorsal. Snout very much projecting; the margin at bottom, above the upper Jaw, dtvJd~d mt~ 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. Fit·st 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 m01·e. 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 strire behind. B. 7; D. 10-1/25; A. 1/8; C. 17; P. 21; V. J/6. 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 fascire. 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 uppet· 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. FISH. 45 As Cnvier and Valenciennes have mentioned individuals of this species, which varied in the number of rays in the soft dorsal from twenty-two to twentyfour, I cannot but consider the two above described as specifically the same, though in the first these rays amount to as many as twenty-five. This, which is the larger specimen, was taken by Mr. Darwin at Bahia Blanca, where it is said to have been common. The other was obtained at Maldonado. 2. UMBRINA OPHICEPHALA. Jen. U. elongata; rostro obtusissimo, iumido, ltaud ultra fauces producto, ma115ine infe- 1'iore quadrilobato, lob£s intermediis 1·otundatis; fossuld longitudinali inter nares, p1·ojuude exaratd; poris quatuor infra sympltysin; dentibus velutinis, serie externlt in maxilla superiore aculeiformi ,· preoperculo obsolete denticttlato; operculo mucronibus duobus parvis instructo ; spinis dorsalibus tertia et quartd longissimis, corporis altitudinem cequantibus; spina anali gmcili, mdiis articulatis di,midiu breviori. D. 12-1/22; A. 1/9; C. 17; P. 20; V. J/5. LoNG. unc. 6. lin. 6. FonM.-Very much elongated; the greatest depth just one-sixth of the entire length; the head one-fifth. Dorsal line nearly straight. Profile falling very slightly till it reaches the nostrils, when it suddenly becomes vertical. Snout in consequence short, and very blunt, and not projecting beyond the jaws; with a deep broad channel down the middle, extending from between the nostrils to near the mouth : on each side of this channel, the snout is very protuberant. The lower ma1·gin of the snout is divided into four lobes, the central pair of which are rounded: above each of the exterior lobes is one large pore, and an odd one in the middle. There are also four pores beneath the symphysis, and a short barbule, as in the last species. The eye has a diameter about one-fifth the length of the head, and is distant one diameter from the end of the snout. The nostrils, which are immediately in advance of the eye, consist of two round apertures, one before the other, the posterior one double the size of the anterior. Upper jaw a vet·y little longer than the lower. A baud of velutine teeth in each jaw; with an outer row above of moderately strong card, rather curving inwards and backwards, and closer-set than those of the U. arenata, amounting to twenty-eight or thirty in number : there are also some smallet: card teeth behind this outer row passing insensibly into the velutine. Preopercle very obsoletely denticulated. Opercle with two flat points not very obvious. l~Irst dorsal triangular, and moderately high in the point; third and fourth spines longest, about equalling the depth of the body; first spine very small: all the spines rather slender. Second dorsal about half as long again as the first, but the rays are too much broken to judge |