Too minute to examine except under the magnifying-glass, or to attempt to illustrate, we can convey only a general idea of these curious viper scales, which to the touch are spinous, and rough as a coarse brush. They must form an unpleasant perch for a bird, if it be true that the latter is enticed by the horns of some vipers to come and peck at them, as at a worm. These rigid head-scales become gradually larger and more simple on the body, but are still comparatively small for so large a serpent. In some few of the viperine snakes, plates are present as well as the fine scales, though chiefly about the nose and mouth, exceptions which are now and then found in non-venomous ones also. The preceding three illustrations are the head shields of a Colubrine snake, in which a greater uniformity prevails. Below are given four other types, though even here variations are constantly occurring. [Illustration] _Fig. a._ One of the Indian _Crotalidæ_. It has two conspicuous supraciliary shields, two equally conspicuous anterior frontals over the nostril. The rest are small, and those on the top are absent altogether. The scales are all finely carinated. _Fig. b._ The head of a Colubrine snake in which the same scales appear as those in Fig. 1 of the preceding page, viz. two orbitals, etc., but are all much smaller, and do not therefore more than half cover the head. _Fig. c._ The head of a sea snake, which as to design is really pretty, and, as Günther affirms, so different from land snakes in respect to head shields, that without any further investigation an ophiologist can at once distinguish the _hydrophidæ_. _Fig. d._ The head of a viper in which only very small supraciliary and nasal (or anterior frontal) shields are seen. The angular form of the viperine head is here noteworthy. In some of the Tropical American viperine species (the _Crotalidæ_) the angular head is so marked as to be separated into a genus—the _Trigonocephali_, three-cornered heads. One head is sagittate or arrow-shaped to such an extent that the serpent is known as the _Fer de lance_, the dreaded _Trigonocephalus lanceolatus_ of the Antilles. There are _Trigonocephali_ among the Indian Thanatophidia also. One other very remarkable exception must not be omitted—namely, that in pythons may be seen an angular head, which makes the neck thin and conspicuous, only in a less degree; and also the absence of large head shields. In addition to this, many of the pythons have particularly short and very pointed tails—three singular viperine features in non-venomous snakes, which can only be inherited from a common ancestry.