46 
HORN EXPEDITION—MAMMALIA. 
Ornithorhynchus, where, from a common follicular opening, issue four bundles of 
small hairs behind the single large one. 
In the first specimen which came into my hands some years ago I was struck 
with the appearance of a patch of hairs just above the sacral region. They were 
somewhat darker than the rest and more closely matted together, and conveyed 
the impression that they might be associated with the presence of a glandular 
area. Every specimen since examined lias shown exactly tlie same appearance, 
and sections through this region show that a curious modification of the hairs is 
present. The groups of follicles run down to a much greater depth than else¬ 
where, so that in either transverse or longitudinal section the appearance is 
presented of a pad-like structure about 10 mm. in diameter, which gradually thins 
off at each side. This pad is made up of the long and very closely-set groups of 
hair follicles, each group consisting of a large number of fine and a single large 
flattened hair. 
Examination of the hairs shows that the larger ones are somewhat shorter in 
this part than the fine ones, and that their ends are always broken up into from 
two to six very slightly divergent stiff, pointed branches. These, as it vvere, 
entangle the fine hairs, and so produce the matted appearance. 
This modified area is more prominent in dried than spirit specimens, looking 
in the former like a rather dirty patch where the fur has been pressed down. It 
is difficult to attach any meaning to its presence, but its constant development 
would seem to indicate that it must serve some special purpose. 
Teeth .—In his paper “On the Systematic Position of Notoryctes typhlops"* 
Dr. Gadow, from the examination of nine specimens, said :—The full number of 
4 
.31 ’2 
teeth seems to be ‘-. c. -. p.m 
O 1 
2 - 4 - 
The full number of teeth in each 
jaw according to this being ten. 
There is, as Dr. Stirling and Dr. Gadow have pointed out, considerable 
variation in the number of teeth in front of the molars, which appear to be always 
four in number in both the upper and lower jaws. 
As this question will be more fully dealt with by Dr. Stirling and myself, I 
will only say here that the full number of teeth in each jaw is eleven, but that in 
none of the thirty specimens which I have so far examined has there ever been 
the full number present in both jaws. 
* Proc. Zool. Soc. London, May 3,1892, p. 301. 
