Gillichthys mirabilis- -Barlow 
65 
flexure per fish is not uncommon. Photographs 
with X-rays indicate that the structure of the 
vertebrae has broken down at the apex of the 
more extreme curvatures. Whether there is a 
disintegration and/or fusion of the vertebrae is 
not clear from the photographs. 
The occurrence of axial deformities increases 
during the hottest months of the year (Table 
8). During July, the incidence of twisted speci- 
mens increases from around the usual 25% to 
30'%. The maximum occurs in the period of 
October to December. (The very high value 
for October is based on a small sample and 
therefore is subject to greater errors of random 
sampling. There is also a serious problem in 
obtaining a truly random sample, because of 
the sudden appearance of deformities in the 
young fish.) 
Axial aberrations usually are manifest for the 
first time in subadults during August, the peak 
of the hot season. There is no relationship be- 
tween size and incidence of deformities in these 
young fish. The deformities appear during the 
same period of time but not at a given size. 
Axial deformities are also apparent in the 
sciaenid fishes that have been introduced into 
the Salton Sea. Here, too, anterior kyphosis 
seems to be prevalent. 
Other abnormalities are seen in mirabilis but 
are not as common as the axial terata. These 
include forward projection of the lower jaw 
(Fig. 13), dermal flaps on the upper jaw, and 
pronounced elongation of individual rays in 
the median fins. 
DISCUSSION 
Body Form 
Differences in size and shape are apparent 
in comparisons between various kinds of fishes 
from waters of different temperatures. Almost 
invariably in the Northern Hemisphere, the 
more northern representatives of a species or 
of a genus are larger than those to the south 
(Hubbs, 1926: 60; Vladykov, 1934: 120). The 
changes in body proportions have not been as 
thoroughly investigated, but some tentative gen- 
eralizations can be made. Northern, slowly grow- 
ing races of a species usually have smaller heads, 
eyes, maxillas, and fins than do their southern 
counterparts, although opposite effects are not 
uncommon (Hubbs, 1926: 62; Vladykov, 1934: 
118; Martin, 1949: 23; and included refer- 
ences ) . 
Morphological differences in Gillichthys mira- 
bilis, as indicated by lines fitted to part lengths 
versus standard length, are apparent between 
the aggregates of populations from the Gulf of 
California and the Pacific Coast, and between 
the populations within these regions. There is 
no pattern among the regressions (length of 
parts on standard length) which might provide 
a due to the nature of the differences. There is 
only the slightest tendency for the height of the 
anal fin to be greater in more southern popula- 
tions of the Pacific Coast region. 
The Gulf populations differ, for the most 
part, from those on the outer coast in the way 
one would predict for faster developing fish. 
Fig. 13. Gillichthys mirabilis, female, standard length 101 mm, from the Salton Sea, California, and typical 
of extreme terata. Fold below the pectoral fin is from an incision. 
