First among the most brilliantly coloured snakes, of which there are many, stand the Coral-snakes, _Elaps_, of America, mostly annulate with red, yellow or white, and black. This striking coloration obtains also in diverse harmless snakes inhabiting the same part of the world, and this coincidence has been adduced in favour of the theory of mimicry, correlated with that of natural selection, which accounts for the resemblance as being of advantage to a harmless species, which is thus mistaken for one notorious for its deadly poison, and advertised as such by its brilliant colours (warning coloration). But other poisonous and much more dangerous snakes are not, as a rule, endowed with brilliant colours. It is true that these also may have their mimics: the Krait, _Bungarus cæruleus_, and _Lycodon aulicus_, in India, the Pit-viper, _Ancistrodon himalayanus_, and _Psammodynastes pulverulentus_, in the Himalayas and Assam, are good examples of such cases. On the other hand, there are equally striking instances of what one would regard as mimics if they only occurred together; thus, there is no better case of general resemblance between a poisonous and a harmless snake than we find in the Indian Cobra and the _Coluber corais_ of tropical America, where Cobras are absent, or between a Viper and the Boid _Enygrus asper_, from New Guinea, where no Vipers exist. Without attempting to offer any suggestion to account for the similarity of markings which prevails in certain parts of the world, attention may be drawn to the predominance of longitudinal dark and light stripes in the Indo-Malayan representatives of the American _Elaps_, shared by many innocuous snakes of similar form inhabiting the same region, and to the striped tails common to various Colubrids of Madagascar, as if the snakes of a district had agreed to conform to certain fashions in dress. It is further noteworthy, in relation to the theory of warning coloration, that many Uropeltids, innocent burrowing creatures living underground or concealed under stones or rotting tree-trunks in the forests of Southern India and Ceylon, hardly ever showing themselves in daylight, are among the most striking for their bright yellow or red and black markings. We may point out at the same time the very marked resemblance in form and coloration between the Uropeltid _Melanophidium bilineatum_, and the Apodal Batrachian _Ichthyophis glutinosus_, both occurring together in Southern India.