It should be remarked, however, that the Barnegat City specimen does not
agree in color with any of the European or New Zealand specimens. On the
other hand, the latter show a most extraordinary diversity in color, some
being black, with the head and back as far as the dorsal fin white;
others all black above, white below, and the head black and brown. The
color of the young specimen from Buenos Ayres, Argentina, is described by
Burmeister as follows:
All the body of the animal is of a light gray color, a little
yellowish, resembling the color of light ash, but much darker on the
back and much lighter on the belly. The fins are much darker than the
back—almost black—and the large fin of the tail has a very pure white
area of irregular shape on the underside.
If the indications from the skull and proportions are trustworthy _Z.
cavirostris_ must be a species in which the color is very variable,
differing perhaps in the two sexes, or with differences in age. This is,
however, by no means certain at present, and whether the diversities of
color reported in different specimens are merely individual variations,
or are due to post-mortem changes, remains to be discovered. It will be
noticed that the color of the Argentine specimen is nearest to that of
the Barnegat City specimen.