A parietal foramen; scales or bony scutes frequently present, especially on the ventral region, which is further protected by three large bony plates - interclavicle and clavicles, the latter in addition to cleithra.
Sometimes these scales assumed the importance of scutes and formed a carapace, as in the "batrachian armadillo" discovered by E.
Armadillos alone possess an external bony skeleton, composed of plates of bony tissue, developed in the skin and covered with scutes of horny epidermis.
In Central and South America alligators are represented by five species of the genus Caiman, which differs from Alligator by the absence of a bony septum between the nostrils, and the ventral armour is composed of overlapping bony scutes, each of which is formed of two parts united by a suture.
In some specimens of these genera the horny shields covering the bony scutes of the carapace have been preserved, and since the foramina, which often pierce the latter, stop short of the former, it is evident that these were for the passage of blood-vessels and not receptacles for bristles.