6o 
BULIvETIN of the bureau of fisheries. 
Variation in Fin Rays of Lavinia Exiucauda. 
Locality. 
Number of spec 
Dorsal — 
imens having — 
Anal — 
10 
II 
12 
13 
II 
12 
13 
14 
Sacramento River: 
Red Bluff 
0 
8 
6 
8 
6 
Total 
2 
26 
39 
I 
2 
4 
48 
8 
With a decrease of the number of fin rays has come a consequent shortening of the bases of both 
dorsal and anal fins in L. ardesiaca. 
Dorsal and Anal Fin Measurements Recorded in Hundredths of the Length to Base of 
Dorsal. 
Dength base of dorsal 
0. 12 
0. 13 
0. 14 
0. IS 
0. 16 
0. 17 
0. 18 
6 
23 
Length base of anal 
0. II 
0. 12 
0. 13 
0. 14 
0. IS 
0. 16 
0. 17 
0. 18 
0. 19 
6 
14 
Examples of this species are comparatively heavy in appearance, the body being somewhat less 
compressed than that of L. exilicauda, the snout a little longer, and the head somewhat larger. These 
differences, though slight and not easily shown by measurements, appear when a considerable series 
of speeimens of both species pass under one’s observation. 
The structure of the scales (fig. 26, pi. xxiv) does not appear to differ materially from that of 
L. exilicauda. They are more or less spatulate in outline, the nuclear area elevated, the basomedian 
and basolateral ridges high and rounded, the apicolateral ridges very weak or entirely absent. There 
are neither basal nor lateral radii. The apical radii number as follows, 50 scales from 10 individuals 
having been examined : 
First year, 5 to 10, usually 7 to 9. 
Second year, 6 to 16, usually ii to 14. 
Third year, 9 to 22, usually 14 to 19. 
Fourth year, 11 to 26, usually 16 to 23. 
The species is found in the Pajaro and Salinas Basins, but appears to be absent from the San 
Lorenzo. It frequents the lower courses of the streams, delighting in the shallow water of the ripples, 
where large schools may be seen moving about over the yellow sand of the bottom in the full glare of 
the sun. The larger individuals, which are darker in color and less silvery than the smaller ones, take 
