IGUANAS. 109 
Strobilosaura and Nyctisaura of Dr. Gray, or the tribe of the Iguanas 
and their kindred, and that of the Geckos and their kindred. The 
tribe of 
STROBILOSAURA 
Have the scales of the back and sides imbricate, generally rhombic, 
and those of the lower parts imbricate and of small size. Tail with 
more or less distinct whorls of scales. The eyes diurnal, with round 
pupil, and valvular lids. Feet with toes of very unequal length. 
Many of these Reptiles have a row of spines or spine-like scales along 
the back and tail, which in some are very long, while others have 
high dorsal and caudal crests, and an expansile gular pouch. Like 
the Varans among the Leffoglossa (p. 107), these Lizards do not 
renew the tail, or a portion of it, after mutilation. There are 
two great families of them—one peculiar to the Old World and 
Australia, the other to the New World; but they do not differ 
much, and might very well be retained as varieties of the same ex- 
tensive family. 
In the family of /ewanide, all of which inhabit America or its 
islands, the teeth are round at the root, dilated and compressed at the 
tip, and toothed at the edge ; they are placed in a simple series on 
the inner side of the jaws, just below the margin, and are covered on 
the inner side by the gums; as they fall out they are replaced by 
others, which grow at the base of their predecessors. Probably not 
fewer than 150 species are now recognised, which are distributed 
under more than fifty genera. We can only notice a few of the 
most remarkable of these Lizards, some of the larger of which attain 
a length of five or six feet, with proportionate bulk of body. As 
a general rule, the larger species are principally herbivorous, while 
the smaller are generally insectivorous, though many of the latter also 
devour fruit. As most of them are remarkable for their rapid changes 
of colour, the name of chameleon is often misapplied to them, in the 
supposition that the chameleons are the only lizards in which that 
curious phenomenon is observable. Of one remarkable species, the 
Spherops anomalus, inhabiting Brazil, it is stated that the eye nearly 
resembles that of the true chameleons, it is also one of those which 
are particularly celebrated for changing its hue. 
The name Zevana 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 characterised 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, com- 
