LIFE-HISTORY OF AMPHIGONOPTERUS AURORA. 199 



tance within the margin. Thus it appears that considerable 

 growth had taken place since the annulus was formed. The 

 actual amount of this growth (determined by a method discussed 

 later), in 50 of the specimens from near Piedras Blancas, was 

 estimated to have varied from 10 to 28 mm. ; in more than half 

 (28) of these the growth had been 14 to 18 mm., while the 

 average growth computed to have occurred between the forma- 

 tion of the first two annuli of older fishes from the same locality, 

 was about 24 mm. No annulus was found on the margin of the 

 scales of gravid nor recently spent females, indicating that it is 

 not a breeding mark. 



In certain other species of the family, the annuli are doubled 

 in a confusing fashion, suggesting the possibility that two annual 

 checks in growth are registered on the scales, one during the 

 winter and the other during the breeding season. For instance, 

 the scales of a 200 mm. female of Embiotoca laterdlis, taken on 

 June i/, when bearing young, show five typical winter annuli, and 

 in addition to these, and located between them, less distinct but 

 similarly formed rings, the outermost at the extreme margin of 

 the scales. Similarly in Micromctrus minimus the annuli are 

 often closely approximated or doubled (beyond the second winter 

 annulus) ; in these cases also the outermost annulus is located at 

 the margin of the scales of females carrying young. Such a 

 condition is seldom apparent in Amphigonopterus, but may have 

 introduced an occasional error in the interpretation of the scales 

 of the fishes three or four years old. 



The annuli or seasonal rings on the scales of Micromctrus 

 minimus closely resemble those of Amphigonopterus aurora (ex- 

 cept in the more frequent appearance of doubled annuli, as just 

 noted). The outermost annulus is located at some distance 

 within the margin of the scales of yearling specimens taken in 

 late spring and early summer in central California. In several 

 specimens of both sexes, young of the preceding summer, taken 

 at Pt. Loma on December 31, the single winter annulus is on or 

 immediately within, in one male considerably within, the margin 

 of the scale. These facts indicate that the annuli of Micrometrus 

 are winter marks, that the first is formed in December in southern 



