The three sketches are given merely in illustration of a phenomenon which I cannot attempt to explain or even to comprehend. They were drawn from memory, and are not therefore offered as exact representations, though near enough to serve our purpose. The movement seems to argue some peculiar muscular or nervous connection between each pair. The serpent had not been long dead; and as no others of this species have since been at the Gardens, I cannot tell whether the same sympathetic movement would be seen in the living viper. I have attentively watched the horns of the other vipers, but never detected the slightest voluntary action in them. Nor do the horns of V. nasicornis respond to the touch in the same way. A third of the horned vipers is the Cerastes of classic times. Illustrators of books from descriptions only have presented us with this serpent adorned with horns like a young heifer. They are simply scaly appendages like the rest, but when perfect do certainly curve backwards and upwards in a rather bovine fashion. It happened that a Cerastes was brought to the Gardens just after the six-horned viper had died, affording me a happy opportunity of examining it. It was of this viper that Pliny wrote: ‘It moves its little horns, often 4 in number, to attract birds, the rest of its body lying concealed.’ It is the habit of all those inhabiting sandy deserts thus to hide themselves, probably to escape the scorching, drying sunshine, and with perhaps the nose and upper part of the head exposed for breathing. I have carefully watched several of the horned vipers for a long while together, but have never detected the slightest volitional movement in their horns. A bird might come and peck at them, nevertheless. Another belonging to South Africa (Lophophrys) has a bunch of irregular and much shorter horns standing erect and apparently unpaired. Incipient horny scales often accompany the regular pairs, making it difficult to decide exactly which was Pliny’s of the ‘four horns,’ and which is the Hexacornis of Shaw. Varieties exist and add to the perplexity; probably also hybrids occur among these as among non-viperine snakes.
A curious variety of the nasal appendages appears in the Langaha with the crête de coq; only the crest is on the snout instead of on the head.
These spurs are merely modifications of the epidermis like the rest; but are, no doubt, endowed with peculiar sensitiveness, so that possibly they act as a sort of herald in the dark, like a cat’s whiskers.
Profile of Langaha.
There are the pointed-nosed Dryophidians also, with scaly protuberances, and others with variously-elongated snouts terminating in long, scaly, horn-like appendages, all, no doubt, more or less sensitive, to enable the owners to feel their way, or ascertain the nature of their surroundings, especially if they are of nocturnal habits.
In some of the tree snakes, notably Passerita, there is no appendage, but the long snout is itself endowed with mobility. This is a nocturnal snake; a harmless and exceedingly slender, graceful creature.
Profile of Passerita.
But of these curious developments or prolongations, one of the Indian fresh-water snakes presents a remarkable example, almost allying it to some of the fishes with long tentacular appendages. Herpeton tentaculum is its name, its pair of tentacles being scaly and flexible, and in appearance somewhat like the African viper’s horns, sticking out horizontally from its snout. They are employed under water as organs of touch, and probably to discern food.