244 PROCEEDINGS OF THE ACADEMY OF [April, 



nal phalanx of the pollex,*' and the jugalis propatagii extending in 

 Galeopithecus from the external auditory meatus and malar bone 

 to the finger and palatopatagium are homologous and are supplied 

 by'the same nerve, the facial. The coraeo and huniero-cutaneous 

 nuiscles, among others, agree essentially in their disposition in 

 Galeopithecus and Chiroptera. Further, the striking fold in the 

 palatopatagium of Galeopithecus, extending to tiie yentral surface 

 of the elbow, is an equally characteristic feature in the patagium of 

 the Chiroptera. It Avas absent, however, in the two specimens 

 of Pteropus fmgivorous dissected by the author. It should be men- 

 tioned, however, that in the uropatagium of the Chiroptera mus- 

 cles are present that are absent in that of Galeopithecus, such as 

 the cutaneo, pubic, ischio and femoro-cutaneous. On the other 

 hand, in Petaurus, the muscular fibres of the patagium ai'e so little 

 differentiated that they cannot be homologized with those of Galeo- 

 jntheciLS or Chiroptera, while in Pteromys muscles are present in its 

 patagium that have no homology in Galeopithecus or Chiroptera.' 



Such being the relation of the patagium of lemurs, marsupials 

 and rodents to that of Galeopithecus and bats, it is readily con- 

 ceivable how, on the theory of descent, the patagium of Pteropus 

 might be derived from that of Galeopithecus by the simple exten- 

 sion of the upper extremity, supiwsing that such extension was of 

 advantage in the struggle for life, and that the variation, however 

 acquired, was intensified in successive generations. While it does 

 not necessarily follow that because two animals found in the same 

 part of the world and provided with the same kind of patagium 

 and having similar habits should be genetically related, it seems 

 more probable that Pteropus, the more specialized animal, should 

 have descended from Galeopithecus, the more generalized one, than 

 that the two animals should have acquired such characteristic struc- 

 tures and habits independently of each other. 



In regard to the nuiscles of the head and neck, it may be men- 

 tioned that the part of the trapezius arising from the head and 

 neck in lemurs and insectivores is absent in Galeojnthecus and 

 bats. The insertion of the teres major is quite distinct from that 

 of the latissimus dorsi in Galeopithecus and Chiroptera, the action 

 of the former muscle being to reinforce that of the subscapu- 



« Macalester. Myology of the CheirojJtera, Phil. Traus., 1873, p. 128. 

 ^ Macalister, op. cit., pp. 14-21. 



