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Show 1873.] CHARACTERS IN THE CHIROPTERA. 243 glandular eminences on either side is probably more connected with season. In a large number of male specimens of P. larvata, Horsfield, from Burma, obtained at the same time, in which the testes lie in a false scrotum formed by the skin of the perinaeum, the glandular eminences on either side of the frontal sinus are not more developed than in the females ; while the frontal sac is very large, contrasting remarkably with the rudimentary one in the other sex. In a specimen from the Kasia hills, in which the testes occupy the abdominal cavity, the frontal glandular eminences are greatly developed (as shown in fig. 3), and their development is evidently Fig. 3. Fig. 4. Phyllorhina larvata. Phyllorhina speoris. connected with season; for, in the Chiroptera and some genera of Rodentia and Insectivora the testes, during the rut, pass into the abdominal cavity *. In P. larvata and P. speoris the external margins of the frontal sac are, in the males, greatly swollen, naked, and elevated considerably above the surface ; while in the females the margins of the slight depression in the skin of the forehead, corresponding to the frontal sac in the males, are not more thickened or elevated than in young males of the first year. This is well shown in the illustration above (fig. 4). In other species, where thickening and elevation of the margins of the frontal sac, or enlargement of the neighbouring glandular prominences do not exist, a permanent secondary sexual difference is found in the depth of the sac, which, in the most adult females, is a mere shallow depression in the skin of the forehead. The above described remarkable difference between the males and females of P. larvata and of P. speoris, taken with a slight difference in the colour of the fur, has caused more than one distinguished zoologist to separate the males and females into distinct species f. It is difficult to assign a use to this protrusible frontal sac. The only other animals possessing apparently homologous organs are the * See Wagner's ' Comparative Anatomy,' ed. Tulk, p. 56. t Thus tbe species P. insignis and P. deformis were founded on male and female specimens respectively of P. larvata; and, similarly, P. apiculatus and P. penicillatus on P. speoris. (For synonymy see Peters in ' Monatsbericbt Berlin Akademie,' June 1871, p. 320; also Blyth, Journ. Asiatic Soc. Bengal. vol. xiii. p. 481.) ' 16* |