14 H. W. MARETT TIMS. 
progressively increase, that between pin* and m’ being of considerable width. Pm’ is 
a comparatively small tooth, while the remaining premolars are sub-equal ; if anything, 
pm is slightly the largest of the series. From the fact that the Phocine still retain 
the characteristic number of three incisors in the upper jaw, it may be presumed that 
the loss of an incisor in the Monachine has taken place comparatively recently, and 
the question arises, which of the three is the missing tooth? Comparison with other 
mammals, e.g. Rodents and Marsupials, affords no clue, since the tooth differs in both 
these orders. I have, therefore, examined serial sections of the upper jaw in these 
seals at different ages in order to try and determine this point. 
In a specimen with a body length of 147 mm. (No. 17), I found what I believe to 
be distinct evidences of three upper incisors. Of these the first and third were con- 
‘1 
: : : U 3s : 
siderably larger than the vestige of the intervening tooth, — already giving evidence of 
calcification. A consideration of the facts appears to lead to the conclusion that it is 
the second incisor which is missing in the adult. If this conclusion be correct, it tends 
y2 
: : uv. 
to support Mivart’s opinion of a Lutrine origin for the seals, for in Lutra itself — is the 
smallest of the series, and in many cases this tooth is so crowded out that it occupies a 
position quite behind the other incisors. Mere inspection of the teeth would lead to 
2, 
the conclusion that ~ is in process of extinction among living Otters. 
So far as I have been able to determine, the tooth-genesis in the seals affords no 
distinct evidence as to their phylogeny. 
It is well known that the milk dentition of the seals is but feebly developed, 
and it is generally stated that the teeth belonging to that series are usually shed just 
before or very shortly after birth, From an examination of these jaws, I am of 
opinion that many of the deciduous teeth either do not all develop beyond the stage 
of a non-calcified enamel organ, even if so far, or else if they attain a stage of 
calcification that they disappear at an earlier age than is usually supposed. 
2 
In the jaws here figured the only milk tooth which was present was Ae 
Further detailed investigation would no doubt settle these points, but I have not 
deemed the matter of sufficient general importance to work through all the material in 
the present instance, though I hope I may be permitted to do so on a future occasion. 
As already mentioned, owing to the curvature of the vertebral column in the 
cervical region, the cesophagus is deflected to one side. 
There is a considerable amount of black pigment present in the mesentery and 
peritoneum generally. In the dorsal part of the cavity it is present in so large an 
amount as to give the peritoneum in this situation an almost uniformly black 
appearance. 
The greater part of the stomach lies to the left of the mesial plane; it is relatively 
broad, so that the organ has an almost globular shape. The liver becomes more 
multilobed as age increases, the individual lobes exhibiting a considerable amount of 
