EOSS' SEAL. 49 



Nor is there in Macrorhinus any marked development of spots or splashes, 



and in this Ommatoplioca 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 



Cystopliora ; 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 Cystophorinse than with the Stenorhinchijise, 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 



2 2 2 2 



reduced to , they should again revert to ^ ^ , 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 Stenorhinchinfe. 



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 to a certain point, being blackish grey in general 

 tone, when freshly moulted, darkening consideral)ly 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. 235-243, 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. II. E 



