The name _Iguana_ was given by Laurenti to a heterogeneous group of Saurians, various forms being included which were first separated by Daudin. The Iguanas, as thus restricted, are characterized by a very large thin dew-lap under the neck, a double row of small palatal teeth, and a crest on the back and tail; the latter long, slender, compressed, and covered with small imbricated and carinated scales. Messrs. Duméril and Bibron describe the genus, thus modified, as principally remarkable for the cutaneous prolongation which constitutes the deep and thin dew-lap, or pouch, the free border of which describes a curved line, and is dentated at the part nearest the chin. The head is moderately long, and has the form of a pyramid with four faces. The neck is slightly compressed, the limbs long, the toes unequal and sometimes denticulate on the edge. The five toes of the posterior feet are graduated; the tail, which is long and slender, is slightly flattened from right to left. The Iguanas live chiefly on trees, but they take readily to the water, swimming with great facility. There are numerous species, all of which are found in South America and the Antilles. In the Island of Isabella, Sir E. Belcher found swarms of them which he had reason to consider omnivorous, feeding voraciously on birds' eggs and the intestines of birds and insects. The Common Iguana, _I. tuberculata_, which inhabits a great part of South America, is one of the best known species of this family. These reptiles are easily recognised from the large pouch underneath the neck, and the dentated crest which extends from the head to the extremity of the tail. The tail, feet, and body are covered with small scales. On the upper part, their colour is a more or less decided green, sometimes becoming blue, at others slate-coloured; the lower part is of a yellowish green. The sides present zigzag, roundish, brown scales, edged with yellow; frequently a yellow line is traced obliquely in front of the shoulder, and some individuals are sprinkled with brown; others have the limbs spotted with brown on a black ground. The tail is surrounded with brownish rays alternating with others green and yellow. When full grown it attains the length of four feet, but the more ordinary length of the animals is about thirty inches. They are very gentle creatures, and perfectly harmless, feeding almost exclusively on vegetables. They are hunted in America for their flesh, which is excellent; and they are especially common at Surinam, in the neighbourhood of Cayenne, and in Brazil.