General aspect. Xenopeltis unicolor Reinwardt is a burrowing snake, living in South East Asia and in Indonesia. It is easily recognisable even at first sight, both by its peculiar colouring and by the shape of the head, which shows a dorso-ventrally flattened snout, with a curiously rounded frontal margin. Haas (1930) is right in stating that there is probably no other snake with such a remarkable 'physiognomy'. In its way of moving around it seems not to lift the head before going on, but rather to shove it sideways to right and left and then proceed on its way. The scales are very flat and make a completely smooth covering for the animal, this being considered another adaptation to the burrowing life. The name Xenopeltis, however, does not refer to this particularity, but as pointed out by Mertens (1943) to the presence among the headshields of an interparietal surrounded by four parietals, an unusual feature. The trivial name unicolor points to the uniformity of design from head to tail in fullgrown specimens. In the living animal, as far as my experience goes, the most vivid impression is not one of uniformity or monotony, but one of incessantly changing iridescence with an undertone of violet grey; an impression which it is hard to render into words. It is even difficult to convey by means of a photograph: in most of these the white lining of the scales becomes too much enforced and so they give more the idea of a geometric design, a succession of separate squares or lozenges instead of the impression of smoothness of movement and fluidity of colour which predominates in the living animal. Smith (1943) describes the animal as black to chocolate-brown above,