A second series occurs in those _Teidæ_ which have a collar of large shields on the throat. As many as five genera of them have been established, each upon a single species, and all are from intertropical America. In _Crocodilurus lacertinus_ the two rows of crests along the tail recall to mind the Crocodiles, whence the name bestowed. Others have been styled Dragons, as the Great Dragon, _Ada guianensis_, and the Smaller Dragon, _Custa bicarinata_. All bear a certain amount of superficial resemblance to the Crocodiles, and the Great Dragon grows to six feet in length, and is found in many parts of South America. This large reptile runs up the trunks of trees with facility, is quick when on the ground, and it also swims, though not particularly well. It preys upon such small animals as it can manage to seize, and chiefly frequents the inundated savannahs and marshy localities, where it is seen basking in the sunshine; but there is considerable difficulty in taking this Lizard, as it makes generally for its burrow in some raised spot, and bites desperately in self-defence. Its flesh is eaten, and is considered a delicacy. Its eggs, also, are considerably esteemed at Cayenne and other places, and each female lays some dozens of them. The family of _Helodermidæ_ is founded on a very remarkable Lizard from Mexico, the _H. horridum_, which is of the same size as the Great Dragon, and in some respects approximates the following Old World family of _Varanidæ_. Its back and sides are covered with oblong, hexagonal, very convex and shield-like scales, and the belly with oblong, rather convex plates; tail cylindrical, with oblong, convex scales above, and flat, elongate, thin plates beneath. The head is somewhat flattened, and is covered with polygonal, convex shields; the muzzle is rounded; and the teeth are on the inner side of the jaws, incurved, with a groove on the front of their inner side. The bite of this reptile is said to be severe.