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U. 8. P. K. R, EXP. AND SURVEYS ZOOLOGY GENERAL REPORT. 



drawn from the origin of the dorsal, and the same line would pass immediately &quot;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 : Y ; D X, 24 ; A III, 29 ; C 4, 1, 6, 6, 1, 3 ; V 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 Amphistichus similis, size of life. 



Fig. 6 is a section across the line of greatest depth of the body. 



Fig. V, 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. 



