the palate are two rows of similar teeth: there are no poison-fangs. The hind head is more or less bulging, the body, swelling towards the middle, somewhat compressed, not very lengthened, tapering to the tail, which is short and prehensile. One lung is but half shorter than the other. The body is clothed with imbricated scales, as is also the head,—at least, the hind head: the under surface of the body and tail, however, is covered with scaly transverse plates, arranged in a single series on the body; but on the tail, single in some genera, and in others double.
But that which is most characteristic of the Boadæ is the presence of two hooks or spurs, situated one on each side of the vent. These are undoubtedly of great use to the reptile, as helping the prehensile tail to maintain a firm hold
VENT AND HOOK OF BOA.
on the branch of a tree, from which the long body depends, with the head bent up a little above the ground, watching for the approach of prey. But these spurs are undoubtedly the rudiments of posterior limbs, the bones of which, very minute and imperfect, it is true, are detected
