1902.] NATURAL SCIENCES OF PHILADELPHIA. 243 



like a cloak. AVliile asleep, Avliich is usually diurnal, Galeopifhe- 

 cus, so enveloped, hangs head downward, suspended by its hind 

 claws from the branches of a tree, and in that positioi) strikingly 

 resembles Pferojnis when in the same condition. The patagium of 

 Galeopitheeus is not a mere cutaneous expansion or parachute which 

 serves to break the fall Avhen the animal descends from higher to 

 lower levels, but being supplied with muscles and nerves it enables 

 the animal (to some extent at least) to fly and to guide itself. That 

 most competent observer, Wallace, writes: " Once, in a bright 

 twilight, I saw one of these animals run up a trunk in a rather open 

 place, and then glide obliquely through the air to another tree, on 

 which it alighted near its base, and immediately began to ascend. 

 I paced the distance from the one tree to the other, and found it to 

 be seventy yards; and the amount of descent I estimated at not 

 more than thirty-five or forty feet, or less than one in five."* 



While Propithecus among lemurs, Petaurus among marsupials, 

 and Pteromys and Anomalurus among rodents, are also provided 

 with a patagium, the latter differs in all these animals from that of 

 Galeojnthecus in being much less developed, supplied with a different 

 set of muscles and nerves, and is more hairy. The patagium of the 

 above-mentioned animals is therefoi-e not homologous with that of 

 Galeopitheeus, but rather analogous. On the other hand, the 

 patagium of the Chiroptera in being as extensively developed and 

 supplied by the same muscles and nerves is homologous with that of 

 Galeojnthecits, even though the calcar or elongated bone or cartilage- 

 attached to the inner side of the ankle-joint, which supports the 

 patagium in the Chiroptera, is absent in Galeopitheeus. 



While the scope of this communication does not admit of a 

 detailed account of the muscles and nerves of the patagium of 

 Galeopitheeus and allied forms, the following may be cited as illus- 

 trations, among others, of how closely the patagium of Galeopi- 

 theeus resembles that of bats and differs from that of marsu[)ials, 

 lemurs and rodents. It has been shown by Leche^ that while 

 the disposition and nerve supply of the Platysma myoides is the 

 same in Galeopitheeus and Chiroptera, in Pteromys the muscle is 

 absent. Further, it appears that the occipito-pollicaris or the 

 muscle extending in Chiroptera from theoccipifal bone to the termi- 



* Malay ArcMpeUujo, 1869, p. 145. 

 » Op. cit., pp. 14-18. 



