Gillichthys mirabilis— B arlow 
51 
not known whether or not they spawn this late 
in the season. In the Salton Sea, the first spawn- 
ing occurs in January and the last in May or 
June. Postlarvae of mirabilis have been collected 
in early February in the northern and central 
Gulf of California. There are no data available 
on the length of the spawning season in Gulf 
populations. 
Depending on the size of the female, 4,000- 
9.000 eggs are laid at each spawning (Weisel, 
1947: 80). Weisel believed that each female 
spawns once, rarely twice, in a season. Exami- 
nation of ovaries of Salton Sea fish leads me 
to believe that each female mirabilis oviposits 
2 or 3 times each season, with an interval of 
40-50 days between spawnings. MacGinitie 
(1939: 500) reported that the related blind 
goby, Typhlogobius calif orniensis Steindachner, 
spawns twice during one season, with an inter- 
val of about 2 months. Females of a more dis- 
tantly related goby, the mapo, Bathygobius sopo- 
rator (C and V.), can repeat a spawning in 7-16 
days (Tavolga, 1954: 432). If the above esti- 
mates are correct, each female Gillichthys mira- 
bilis has a potential production of about 8, GOO- 
27. 000 eggs in one season. 
The young of mirabilis reach maturity by the 
end of their first year. Rate of growth was in- 
vestigated only at the Salton Sea. It is clear 
from these data and from the changes in size 
composition of collections from other locations 
taken at different times of the year, that most 
fish attain adulthood and a standard length of 
100-140 mm by the end of their first year. 
Nothing is known of their life expectancy. 
MATERIALS AND METHODS 
In the preliminary analysis of mirabilis and 
seta, certain counts and measurements were se- 
lected as being especially promising (Barlow, 
1961a). While investigating these, other useful 
characters also came to light. 
All counts and measurements, except one, 
were carried out in accordance with the methods 
of Hubbs and Lagler ( 1949) . The exception, 
the height of the anal fin, is defined here as the 
distance from the base of the last element of 
the anal fin to the tip of the second to last ray, 
when the fin is erect. 
The study was based almost entirely on speci- 
mens deposited in the Fish Collections of the 
University of California, Los Angeles. About 
4,000 specimens of mirabilis were examined. 
The fish from San Francisco Bay ( Alviso ponds ) 
were obtained from Sim’s Bait Shop, Long 
Beach, California, and care was taken to verify 
the original source of this material. After fixa- 
tion in 10% formalin, the specimens were 
washed and placed in 46% isopropyl alcohol. 
Statistical Methods 
The purpose of each statistical test in this 
paper is solely to accept or reject a hypothesis. 
The decision to accept or reject a hypothesis was 
based on the 5% critical level, to minimize type 
II errors (Hoel, 1954: 33). Acceptance of a 
hypothesis such as equal means, however, merely 
indicates no detectable differences and does not 
imply that the populations in question are 
proven to be the same. Critical values usually 
are given; the subscript notation 0.95 refers to 
a one-tail test, and 0.975 to a two-tail test. 
Four kinds of tests were employed. The F-test 
was used when the hypothesis involved the 
testing of two variances. Covariance was applied 
to problems when two or more regressions ( fit- 
ted by least squares) were tested at the same 
time. Decisions to accept or reject differences 
between two means were determined by /-tests. 
Correlation coefficients were evaluated as out- 
lined by Hoel (1954: 124). 
Obvious differences were not tested. When 
several variances or means were compared, the 
two most divergent values were examined first. 
If no significant differences were revealed, the 
others were not tested. 
The statistical parameters of the fin ray counts 
are presented graphically. The format is that 
of Hubbs and Hubbs (1953). Unless the sep- 
aration between means was patent, no statistical 
inferences have been drawn from these figures. 
RESULTS 
Head 
The head of fish from the Gulf of California, 
as seen from the side, is more pointed than in 
Pacific Coast specimens. In this respect the Gulf 
populations approach seta. The difference in 
