BLAKE — ON SKULLS OF FOSSIL MUSK-DEEE. 
33 
The functional interpretation of this singular diversity of organiza- 
tion in animals otherwise so nearly allied to each other, may not be 
manifestly apparent to the philosophical zoologist. It was satisfac- 
torily ascertained in the year 1886 * by the observations of Messrs. 
Bennett, Owen, Ogilby, and Hodgson, that the suborbital sinus sub- 
served a purpose connected with the generative functions, being 
dilated and swollen at certain periods of the year. But the connec- 
tion of the development of the glandular structure of the carneous 
lacrymal sinus with the degree of ossification to which the cheek- 
bones extend is not obvious. If however we suppose that the large 
periodical swelling which, according to Mr. Hodgson, forms a huge 
lump of flesh bigger than, and like in shape to, the yolk of an 
egg, increases periodically in its dimensions, its backward pres- 
sure towards the cheek-bone would be seriously impeded by a bony 
wall, such as we find in the TraguJus pi/gmceus or the AucJienia Vicuna. 
The aponeurotic fascia which fills the lacrymal interspace in the 
Hyomoschus aqnaticus, or the Auchenia Hiianaca, would, however, 
yield more easily, and thus those species would in certain seasons 
have a greater development of their suborbital sinuses. 
Mr. Ogilbyt laid down the theory " as a general remark, which 
however he stated was not universal, that in intertropical animals 
the lacrymal sinus is larger than in more northern species, and in 
those whose range is limited to mountainous districts." This incom- 
plete induction may be considered partially corroborated by the oste- 
ology of the Llamas. In the three varieties, Guanaco, Llama, and 
x\]paca, a more or less large " sublacrymal lacuna" is left. Li the 
Vicuna, ossification has extended to such a degree as to close this 
completely up. How does this singular fact bear upon the theory 
that there is a relation between the gregarious habits of those ante- 
lopes and musk-deer which frequent the plains, and the presence of 
the lacrymal sinuses, and consequent non-ossification of the cheek- 
bones ? The species of Auchenia which has no lacuna, is confined 
to the most elevated table-lands of Bolivia and Xorthern Chile. The 
three varieties in which large lacunae are exhibited, are found over the 
whole Andian range, the (xuanaco supporting life alike under the 
tropical sky of New Granada, or the frozen steppes of Patagonia. 
In this species we find a large development of the lacrymal inter- 
space. But both the Guanaco and Vicuna are gregarious. It is 
therefore quite clear that the development of the lacrymal sinus, or 
the degree to which the lacrymal and other cheek-bones are ossified, 
have no reference whatever to the gregarious or solitary habits of the 
species. This was sufficiently proved by the table which was sub- 
mitted by Professor Owen to the Zoological Society (Proceedings, 
1836, p. 36), in which it was conclusively shown that no constancy 
or correlation existed with respect to the presence or absence of the 
suborbital sinuses. And the facial interspace seems an equally in- 
YOL. T. 
* Proc. Zool. Soc. 1836, p. 34. 
t Proc. Zool. Soc. 1836, p. 38. 
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