CHAPTER XVIII.
THE INTEGUMENT—‘HORNS,’ AND OTHER EPIDERMAL APPENDAGES.
HAVING decided that in animal organization nothing exists without its especial use; assuming also that the peculiar development of cuticle forming the rattle is to supply the deficiency of voice, we are next induced to examine those other appendages in serpents which are also modifications of the integument, such as the ‘horns’ of the Cerastes, the tentacles, snout-protuberances, and developments occasionally seen about the head of snakes, and which have all, no doubt, their uses.
‘Serpents are naked,’ says Günther—that is, they have no separate epidermal productions in the way of fur, feathers, hair, or wool, and all the variations of form in scales are but the folds of the epidermis.[90] The ‘variations of form’ include, therefore, the appendages above mentioned.
The heads of most snakes are covered with non-imbricated plates or shields. The form and position of these shields are in a great measure used in classification; ‘are of the greatest value for distinction of species and genera.’[91] For this reason each and all of the head shields are specially named.
Ophiologists differ slightly in distinguishing them as regards assigning the exact position of some of the shields, which, like all other ophidian features, vary in closely allied species. As, for example, while one naturalist may decide that a certain shield is exactly over the eye, another may consider it somewhat to the right or the left.
Günther’s classification being the one now generally adopted, I copy the names assigned by him, and the diagrams given in his work.
Fig. 1. Top of the head of a Colubrine snake. r, rostral; f’, anterior frontal; f, posterior frontal; v, vertical; s, supraciliary; o, occipital; t, temporal.
Fig. 2. Profile of the same. t, temporal; p, posterior ocular or orbital; a, anterior ocular or præorbital; l, loreal; n, nasals; uu, upper labials; **, lower labials.