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.
TYPE OF ZIPHIUS SEMIJUNCTUS (COPE).
The type-specimen of Ziphius semijunctus (Cope), as already mentioned, is a young female.[38] The most noticeable characters which it presents are that the premaxillæ are flat proximally, and that the teeth are small, sharp-pointed and open at the roots. The form of the teeth is undoubtedly due to immaturity, but as the shape of the premaxillæ is similar to that found in the nominal species gervaisii, it might be thought necessary to refer semijunctus to the latter species. As will be shown later, however, this form of the premaxillæ appears to be characteristic of the adult female of cavirostris, and of immature individuals of either sex, the young, as in many kinds of animals, resembling the adult female rather than the male.
I have been able to find but one character in the skull of semijunctus which might be regarded as specific. This is that the lachrymal bone is thick distally, and cut off square at the end. In other specimens of Ziphius examined it is thin and flat, and rounded or pointed at the end. As there is much individual variation in the form of the lachrymal, this peculiarity alone is, in my opinion, an insufficient indication of the validity of the species.
COMPARISON OF SKELETONS.
A comparison of the skeletons of the three individuals from the Atlantic coast of the United States reveals a number of differences of more or less importance. Were it not for the lack of reliable differences in the skulls, it might be considered that these variations in other parts of the skeletons indicated specific difference. I am disposed, however, since the Barnegat and Newport specimens are of opposite sexes, to regard them partly as sexual and partly as individual. In the case of the Charleston specimen (semijunctus), the skeleton, besides being immature, has been very much damaged by careless handling, and nearly all the bones are somewhat abraded. It is, therefore, only available to a limited extent for purposes of comparison. As no description of a Ziphius skeleton from the coast of the United States has, so far as I am aware, been published hitherto, and as descriptions of skeletons of Old World specimens are few and rather brief, I shall give below a detailed comparative description of the American specimens. For the sake of brevity, I shall refer to each specimen merely by the locality.
VERTEBRAL COLUMN AS A WHOLE.
The vertebral formula in the three North American specimens and in four Old World specimens and Burmeister’s Argentine specimen is as follows: