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 1836 * by the observations of Messrs. 

 Bennett, Owen, Ogilby, and Hodgson, that the suborbital sinus sub- 

 served a purpose connected witli 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 Tragidiis f ycjmcBUS or the Auclitnia Vicuna. 

 The aponeurotic /<75cm which fills the lacrymal interspace in the 

 Hyomosclius aquaticus, or the AiicJienia Huanaca, 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- 

 olog}'- of the Llamas. In the three varieties, Guanaco, Llama, and 

 Alpaca, a more or less large " sublacrjmal lacuna" is left. In the 

 Yicuna, 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 Northern Chile. The 

 three varieties in which large lacunae are exhibited, are found over the 

 whole iVndian range, the Guanaco 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. Y. 



* Proc. Zool. Soc. 1836, p. 34. 

 t Proc. Zool. Soc. 1836, p. 38. 



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