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Show 228 MR. R. SHELFORD ON " FLYING" SNAKES. [Mar. 6, since in tropical jungles tree-trunks are more or less swathed in lianes and parasitic creepers, the climbing of them presents no special difficulty even to a limbless animal. Descent from a tree by way of its creeper shrouds, we may suppose, is even more easy, and is doubtless often resorted to. Some snakes, however, have been seen to hurl themselves from the top of a tree and to fall in •writhing coils into water or bushes beneath ; in the Sadong River, Sarawak, I captured a specimen of Tropidonotus maculatus Edel. that was swimming to shore after such a fall from a tree into the river. Individuals of three species have been observed to "fly" out of trees : namely, Dendrophis pictus Gmel., Chrysopelea ornata Shaw, and C. chrysochlora Reinw. M y attention was first called to this habit by a Dyak collector attached to the Sarawak Museum, who brought in one day in 1898 a dead example of Chrysopelea ornata, and averred that he had witnessed this snake shoot out of a tree and descend to the ground at an oblique angle to the tree, its body being kept rigid the whole time of the " flight." Not unnaturally I gave but little credence to this statement, but m y curiosity was stimulated when, some weeks later, a Text-fig. 56. o/-{- -\ -h-a A ventral scale of Chrysopelea ornata Shaw, a, a, hinge-lines. specimen of C. chrysochlora was brought in with the same story. Instructions to bring in these snakes alive were issued, with the result that before very long I was able to test on the living subject the truth of the Dyak's assertions. It must be noted here, that in these two snakes the ventral scales are provided with lateral sutures, or, as I prefer to call them, hinge-lines (text-fig. 56). If a living Chrysopelea be handled, it may be observed that, by a forcible muscular contraction, the ventral scales can be drawn inwards, so that the snake becomes deej)ly concave along the ventral surface (text-fig. 57, B ) ; at the same time there is a slight dorso-ventral flattening of the body: each scale moves on its lateral hinge-lines; when the muscles working these scales relax, the snake re-assumes its ordinary cylindrical shape (text-fig. 57, A). In other words, during the muscular contraction the snake is like a piece of bamboo bisected longitudinally. As anyone can test for himself by experiment, a rod of bamboo will fall to the ground more quickly than a longitudinally bisected rod of equal weight |