The Iguanas 



Key to the North American Iguanas 



I. A row of upright spines on the back; tail with rings of 

 large spines. Genus Ctenosaura. 



Si^e large three to four feet. 



a. Crest extending a little more than two-thirds the 

 length of the back. 



Brown, with blackish cross-bands. ^ 



CAPE IGUANA, Ctenosaurd hemilopha. 



Distribution. Lower California. 



b. Crest extending to the rump. 

 Black, above and beneath. 



BLACK IGUANA, Ctenosaura multispinis. 



Distribution. Southern Arizona to Mexico and 

 Central America. 



II. A row of flat, enlarged scales on back; tail with rings of 

 small scales. Genus Dipsosaurus. 



Si%e small about twelve inches. 



Pale brown, a net-work of darker brown. 



DESERT IGUANA, Dipsosaurus dorsalis. 



Distribution. Deserts of the southwestern United 

 States; Mexico. 



The Cape Iguana, Ctenosaura hemilopha, Cope. As this 

 large species is confined to the Cape Region of Lower California, 

 where it is the only reptile of its kind, it cannot be confused 

 with other lizards. The spiny crest on the back extends but 

 a little more than two-thirds the length of the body on male 

 specimens, barely two-thirds on the female. The tail is covered 

 with alternate rings of very large spiny scales, and small, 

 smooth scales; on the top of the tail the spines are upright, 

 forming a crest, though they are less developed than the spines 

 on the side. 



Colouration. Olive gray, or greenish above, with blackish 

 crossbands on the forward portion of the body. 



Dimensions. Total length, 4 feet; length of tail, 32 inches; 

 greatest width of head, 3 inches. 



Distribution. The Cape Region Lower California. 



The Black Iguana, Ctenosaura multispinis, Cope. General 

 structure similar to the Cape Iguana, but the spiny crest extends 

 farther back to the rump. 



Colouration. Usually uniform black, above and beneath. 

 Four specimens received by the writer were of an intense, jet- 



107 



