ROSS’ SEAL. 49 
Nor is there in Macrorhinus any marked development of spots or splashes, 
and in this Ommatophoca conforms to it rather than to the characteristically 
spotted seals with which it is at present grouped. Nevertheless, it would not 
be surprising to find that the young of Ommatophoca was spotted as is the young of 
Cystophora ; particularly as a tendency to spotting is occasionally found in Macrorhinus. 
In a very great number of ways, therefore, it would appear that Ommatophoca has really 
closer affinities with the Cystophorine than with the Stenorhinchine, notwithstanding 
the apparently decisive judgment given by its dental formula. This I believe to 
be perhaps of less real value than it at first seems to be, owing to the extraordinary 
amount of variation to which even the number of the incisors is subject in every group 
of seals.* Hardly a species but shows by these variations that no hard-and-fast law 
binds them, and the fact obviously means that the teeth throughout the family are 
undergoing rapid changes. In some, as in Ommatophoca, the cheek teeth are on the 
point of disappearing altogether, and it is therefore less surprising to find that the 
canines and incisors are becoming of greater importance to this animal. Is there any 
great difficulty in believing that in such a case, even if the incisors had once been 
reduced to — they should again revert to noms or, indeed, as in one case 
has actually happened, that the reversion should go even farther and produce three 
incisors on one side in both upper and lower jaws? This example alone is sufficient to 
prove that there is no insurmountable difficulty preventing the multiplication of 
incisor teeth. I cannot help thinking that either the young of Ommatophoca, or a 
more abundant series of skulls than is at present at hand for examination, will tend to 
show that this seal is misplaced among the Stenorhinchine. 
In the eleven skins of this animal that have now come under my notice there 
appear to be two definite varieties of colour apart from changes which can be attributed 
to age or moult. Both are identical up toa certain point, being blackish grey in general 
tone, when freshly moulted, darkening considerably towards the middle line of the 
back and becoming almost whitish on the under surface, but with no definite line of 
demarcation between the two. Running backwards, however, from the sides of the 
neck and shoulder are a number of narrow streaks and lines, pale and indistinct, but 
quite constant, and marking the whole of the lateral aspect of the animal almost to the 
tail. Many of these pale lines are unbroken for several inches in the region of 
the shoulder, but towards the middle of the animal’s length become broken and 
irregular. Towards the hinder flippers and the tail the line of separation between 
the darker dorsal and the paler ventral grey becomes more definite, and this de- 
marcation line extends on to the hind limb, sometimes between the fourth and 
fifth digits and sometimes dividing the flipper into equal halves, one dark and the 
other pale. 
* See Bateson, “ Materials for the Study of Variation ” (1894), pp. 235-248, where a number of other examples 
illustrating the same point will be found, and where the variation in each case has been treated in detail. 
VOL, Il. E 
