204 
U. S. P. R. R. EXP. AND SURVEYS—ZOOLOGY-GENERAL REPORT. 
drawn from the origin of the dorsal, and the same line would pass immediately behind the base 
of the pectorals. The tips of both the pectorals and ventrals are posteriorly even. The 
diameter of the eye is contained less than four times in the length of the side of the head. 
The articulated rays of the dorsal and anal fins bifurcate once towards their tip. Those of 
the caudal and ventrals are divided three times, and those of the pectorals twice, with traces of 
a sub-division of a third degree on some of the tertiary branches. 
The formula of the fins is— 
Br. V : V ; D X, 24 ; A III, 29 ; C 4, 1, 6, 6, 1, 3 ; Y I, 5 ; PI, 24. 
The origin of the dorsal groove is situated beneath the eighth dorsal spine, extending to 
about the middle of the soft portion of the same fin. 
The scales (figs. 7-9) are but very little deeper than long. The lateral line is concurrent with 
the dorsal outline ; the scales of which it is composed number about sixty-six. 
The ground color is bluish grey above ; the sides being silvery. The dorsal and caudal fin are 
greyish yellow ; the anal, the ventrals, and the pectorals, dull yellowish. 
The species inhabits the bay of San Francisco, where the specimen figured has been collected. 
Plate XXXVI, fig. 5, represents the female sex of Ampliisticlius similis , size of life. 
Fig. 6 is a section across the line of greatest depth of the body. 
Fig. 7, a scale from the dorsal region. 
Fig. 8, a scale from the lateral line. 
Fig. 9, a scale from the side of the abdomen. 
List of specimens. 
Catal. 
No. 
No. of 
spec. 
Locality. 
When col¬ 
lected. 
Whence obtained. 
Nature of 
specimen. 
Collected by— 
560 
i 
San Francisco, Cal. 
1853 
Lt. R. S. Williamson...... 
Alcoholic. 
Dr. A. L. Heermann. 
