The skin has generally the appearance as if covered with rows of uniform beads; but, on closer examination, these beads, or more correctly, tubercles, prove to have different shapes and are differently set, according to the part of the body which they cover. On the head from the nose up to between the eyes they are flat, irregularly cut, closely joined and adhere completely to the skull. Those following form polygonal eminences, each one separated from the other by a circle of tiny dermal granulations, while behind the eyes on both sides of the head they are larger, semi-spherical and stand far apart. The throat and the nape of the neck are studded with very closely set small tubercles, increasing in size only above the forelegs, whence they extend in well-defined, transverse rows along the whole upper side of the body and the tail. The under side of the latter and the abdomen are covered with tessellated scales of a light-brown and dull yellow color arranged in another handsome pattern. A Heloderma’s head, with its triangular shape, is very like that of a venomous snake; it gives the animal—especially when it is raised in anger—a truly awe-inspiring appearance. The wide-cleft mouth reaches far behind the eyes. These are very small and, like all lizards, provided with eye-lids that close when the animal sleeps. The eye itself has a dark-brown iris, with the round pupil that indicates diurnal or at least semi-nocturnal habits. Between the nostrils, well in front of the blunt nose, is a wide space. The nostrils are so far down as to nearly touch the margin of the supra-labial scales. This position denotes terrestrial habits in reptiles rather than an all aquatic life. For to most of them water is indispensable to their welfare. Thus the Gila Monster shows this structure as it likes to bathe in shallow water, often for many hours at a time. The crescent-shaped openings of the ears are situated not far from the edge of the mouth, between the head and the neck, and are partly concealed and also protected by the overlapping gular fold; the tympanum is exposed. The animal sees and hears well. The remaining three senses are more or less concentrated in the tongue which is one of the most remarkable features of the Heloderma. It is slightly forked at the tips, half an inch wide and two to three inches long; it is dark reddish-brown with a shade of purple. When in rest it is drawn together into a small, conical shaped mass, scarcely an inch in length. But as soon as something disturbs the usual quietude of the animal the tongue is thrown out immediately. In fact, it is used for smelling, tasting, feeling. It is used for measuring depth and distance, for expressing desire and satisfaction; and with what rapidity is this instrument of communication projected and retracted!