324 
U. S. P. E. R. EXP. AND SURVEYS-ZOOLOGY-GENERAL REPORT. 
Syn.— Osmerus, Art. Gen. Pise. ed. Walbaumi ; 1792, 56 ; &, Synon. 1793, 21.—Cuv. Regn. Anim. II, 1817, 162; 2d 
ed. II, 1829 ; &, ed. illustr. Poiss, 257.— Storer, Rep. Fish. Mass. 1839, 108 ; &, Synops. 1846, 197.— 
DeKay, New Y. Faun. IV, 1842, 243.—Cuv. &. Val. Hist. nat. Poiss. XXI, 1848, 36c. 
The following species has so much the general aspect of Argentina that on a former occasion 
we have described it under the latter heading. The argentine tint which pervades over the 
middle of the flanks, a comparatively smaller mouth than in the known species of Osmerus, the 
presence of six branchiostegal rays, and the position of the ventral fins, were as many traits 
which seemingly militated in favor of the genus At gentina. After considering, however, the 
value attached to the dentition in the family of Salmonidae, we have deemed it expedient to 
ascribe said species to the genus Osmerus , in which it was subsequently placed by Dr. W. 0. 
Ayres, of San Francisco. By its small teeth it reminds us of 0. microdon, from Scandinavia. 
OSMERUS PRETIOSUS, G r d. 
Plate LXXY, Fig. 5. (Under the name of Argentina pretiosa .) 
Spec. Char. —Posterior extremity of maxillar bone extending to a vertical line drawn in advance of the pupil. Eye large 
and circular ; its diameter contained about four times in the length of the side of the head. Origin of dorsal fin somewhat 
nearer the extremity of the snout than the lip of the caudal fin. The adipose is situated opposite the posterior fourth of the 
anal. The origin of the ventrals is placed somewhat behind a vertical line drawn from the anterior margin of ihe dorsal Un- 
Scales of moderate development. Upper surface of head and back yellowish ; outline of scales dotted with black. Sides of 
head and middle of flanks of a shining, silvery tint ; lower half of flanks and belly dull yellowish. 
Syn. — Argentina pretiosa, Grd. in Proc. Acad. Nat. Sc. Philad. VII, Aug 1854, 155. 
Osmerus elongalut, Ayres, in Prcc. Cal. Acad. Nat. Sc. I, Dec. 1854, 17. 
The body is gracefully elongated, compressed, fusiform in its outline, the largest specimens 
observed measuring over seven inches in total length, in which the head enters somewhat over 
five times. The eye is large and circular, its horizontal diameter being contained a little over 
four times in the length of the side of the head. The posterior extremity of the maxillar 
bone extends to a vertical line which would pass in advance of the pupil. The origin of the 
dorsal fin is a little nearer the tip of the lower jaw than the base of the caudal fin. The adipose 
fin is situated opposite the posterior fourth of the anal. The caudal fin is shorter than the 
head. The origin of the ventrals is placed somewhat behind a vertical line drawn at the anterior 
margin of the dorsal, their extremities not extending as far as the vent. The pectorals are a 
little more slender and longer than the ventrals. 
Br. VI: YI; D 11 ; A 13 ; C 10, 1, 9, 8, 1, 8; V 1, 8 ; P 1-16. 
The scales are of medium size. The upper region of the head and back are yellowish, the 
outlines of the scales being minutely black dotted. The sides of the head and the middle 
of the flanks are silvery, shining ; the lower part of the flanks and the belly being dull 
yellowish. 
Reference to the figure.— Plate LXXV, fig. 5, represents Osmerus pretiosus, size of life. 
List of specimens. 
Catal. 
No. 
No. of 
spec. 
Age. 
Locality. 
When 
collected. 
Whence obtained. 
Nature of 
specimen. 
Collected by— 
602 
5 
Presidio, Cal......__ 
1853 
Lt. W. P. Trowbridge. 
Alcoholic. 
Lt. Trowbridge..._ 
603 
2 
..do.. 
San Francisco, Cal_ 
1855 
h 
Lt. R. S. Williamson. 
---.do.-.. 
Dr. John S. Newberry.. 
604 
2 
1857 
Dr. W. O. Ayres. 
.-..do_ 
Dr. W. O. Ayres. 
