Of the Indian species of _Crotalidæ_, those minus a rattle, Fayrer says that they are chiefly in Malaya and Indo-China. Many of them, the _Trimeresuri_, are arboreal, and like the foliage in colour. They have the viperine aspect, but are ‘less formidable than their American congeners,’ being of much smaller dimensions. Only one, _Halys_, has anything approaching to a rudimentary rattle, a tail ending in a spine. Of the _Trimeresuri_, the tree species, Fayrer affirms that few deaths are ascribed to them. Some attain to above three feet in length. He thinks a feeble person might die of their bite. They are of a sluggish habit, and lie quietly hidden among the leaves of low bushes and ferns. They will even suffer themselves to be moved without attempting to bite, but one that was pressed to the ground with a stick struck so hard as to break both its fangs. They feed chiefly on insects. Their habits are crepuscular if not nocturnal, and Fayrer does not state positively that they or any of the Indian _Crotalidæ_ are viviparous. Of the principal American _Crotalidæ_ that are not true rattlesnakes, the ‘Bushmaster’ (_Lachesis mutus_) stands first. This is undoubtedly the largest venomous serpent known. In length it equals the Hamadryad; and in thickness, the large African vipers. On looking closely at the illustration of this reptile’s tail (p. 176), it will be seen that in addition to the spine which terminates it, there are several rows of fine, elaborated scales, which under the microscope appear almost as curiously pointed as those on the head of _Vipera nasicornis_. Dumeril thus describes the tail: ‘_Ponctuée, et précédée de dix ou douze rangées d’écailles épineuses, un peu courbées en crochets à la pointe._’ This is the snake called _Crotalus muet_, or ‘dumb rattlesnake,’ by Linnæus, and which is supposed to simulate the sound of the rattle by vibrating this point against the leaves; but many other snakes do this whether their tail is pointed or not, as we saw in chap. xi. Any small thing, such as a twig rustling among dead leaves, would produce the same sound. The near approach of _Lachesis_ to _Crotalus horridus_ of the same habitat is, however, seen in this rudimentary rattle, the agitation of which may similarly be attributed to the timidity of these ‘highly nervous and irritable creatures,’ to repeat Coues’ words; for deadly as they are, timidity strongly displays itself. Watching the venomous snakes when their food is dropped into their cages, their excessive caution, amounting to cowardice, is remarkable, and this with the rattlesnakes especially. One will fix its eyes on the rat which is running about, and shrink back terrified if it approach too closely. Then if the quadruped is a moment quiet, the snake appears to be considering whether it will be advisable to attack it or not. Stealthily and slowly it approaches its head, but on the slightest movement of the little animal, recedes in alarm, and is