102 U. S. P. R. R. EXP. AND SURVEYS—ZOOLOGY—GENERAL REPORT. 
List of specimens. 
Catalogue number. 
No. of specimens. 
Sex and age. 
Locality. 
When collected. 
6 . 
Whence obtained. 
Nature of specimen s 
Collected by— 
370 
1 
Young_ 
San Diego, California .... 
1853 
Lieut. W. P. Trowbridge . 
Alcoholic... 
A. Cassidy __ 
Family ATHERDNTDAE, Bonap. 
The upper arcade of the mouth is formed by the premaxillaries, and the maxillaries, which 
are situated behind, are tapering towards its free or posterior extremity, instead of being 
dilated, as in all the other families, that of Mugilidae excepted. The upper jaw is very pro¬ 
tractile, and the premaxillary and maxillary teeth and others, whenever extant, are generally 
so small as to require to he magnified, in order to become visible. The branchiostegal rays are 
six on either side. There are four gills on either side, hut no pseudo-branchiae. The branchial 
apertures are continuous under the throat. 
The body is covered with cycloid scales, and provided laterally with a silvery band, whilst 
the line of mucous pores is wanting. There are two dorsal fins, widely separated, the 
ventrals being abdominal. The stomach is a simple membranous pouch, without cul-de-sac; the 
pyloric appendages are likewise wanting. The swimmimg bladder, however, is extant. 
Syn.— Jitherinidae, Bonap. Syn. Vert. Syst. 1837.— Grd. in Gilliss’ U. S. N. Astron. Exped. to S. Hemisph. II, 1855, 237. 
The large species of this family are much esteemed as an article of food by all the sea coast 
people. The small ones are equally delicate, although not made an article of commerce, for the 
very simple reason that it is not remunerative. 
ATHERINOPSIS, Girard. 
Gen. Char. —Palate toothless. Gape of the mouth directed obliquely upwards ; jaws even at their extremities ; snout 
rounded or obtuse. 
Syn. — Mherinopsis, Grd. in Proc. Acad. Nat. Sc. Philad. VII, 1854,134; &, in Gilliss’ U. S. N. Astr. Exp. to South. 
Hemisph. II, 1855, 237. 
This genus has all the characters of Atlierina, except that the palate is toothless. The 
structure of the mouth is after the fashion of Mugil: the premaxillaries (intermaxillaries) 
constituting its upper arcade at the exclusion of the maxillaries, which are situated behind the 
latter. The lower jaw is even with the upper ; the gape of the mouth is directed more or less 
obliquely upwards. The latter feature will at once distinguish the present genus from that 
of Basilichtliys, in which the upper jaw projects beyond the lower. 
