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Show ll4 ZOOLOGY OF 'l'HE VOYAGE OF TilE BEAGLE. reach, according to Valenciennes, to the gill-opening, if not beyond it, here only attain to beneath the middle of the eye ; and this character is invariable in five !:ipecimens which Mr. Darwin has brought home. Judging from the description, there would seem to be one or two further differences : the profile appears to be more rectilineal, the pectoral spine shorter, and smoother on its external margin. The colours are on the whole similar, but the pectorals and ventrals darker: the latter, which are said to be yellow in the C. punctatus, are here quite dusky in every one of the specimens. The exact locality in South America in which Mr. Darwin obtained this species is uncertain, as the specimens have lost their attached labels. FAMILY .-CYPRINID.iE. 1. P<ECILIA UNIMACULATA. Val. Poocilia unimaculata, Val. in llumb. Zool. et Anat. Comp. vol. ii. p. 158. pl. 51. fig. 2. FonM.-Body oval, slightly elongated, thick anteriorly, compressed behind. The llorsal and ventral lines meeting at the mouth at an acute angle ; but the head, when viewed from above, broad, and very much flattened between the eyes, and the snout obtuse. Greatest depth about one-fourth of the entire length: thickness two-thirds of the depth. Length of the head nearly equalling, or a little less than, the depth of the body. Mouth small: jaws very protractile; each with a single row of very fine, close-set, pointed teeth ; the lower one a trifle the longest. Eyes large, their diameter three and a half times in the length of the head, high in the cheeks, reaching to the line of the profile. Nostrils consisting of one small orifice a little above and rather in advance of the eyes. Scales large, investing the head and all the pieces of the gill-cover, though very thin and transparent on the opercle and not very obvious there. On the body there are about eight in the depth, and twenty-seven or twenty-eight in a longitudinal row from the gill-opening to the caudal. One taken from the middle of the side found to be of a semi-elliptic form, the exposed portion marked with numerous very fine curved concentric lines, the basal with sixteen or seventeen deeper-cut nearly parallel strire gradually lengthening from the sides towards the middle, but not converging to a fan. Lateral line very faintly marked out by a dotted line, scarcely obvious in some places. D~rsal small, commencing exactly at the middle point of the entire length, measuring this last ~Ult.e to the e~tre~ity of the caudal. Anal similar and opposite; in strictness, however, tcrmmatmg a very bttle m advance. The last ray in both these fins double: the first two in the anal short. Caudal rounded. Pectorals and ventrals small and narrow, the former threefourths the length of the head; the latter not above half the same. 'rhe pectorals, when laid back, reach to the insertion of the ventrals, but the ventrals hardly reach to the commencement of the anal. B. 5; D. 7; A.!>; C. about 24, including short ones; P. 14 or 15; V. 6. Length 2 inches. |