238 REPORT OF NATIONAL MUSEUM, 1898. 



aa. Caudal whorls separated by two or three rows of scales. 



Head short, obtuse; three scales on canthus rostralis; dorsal crest inter- 

 rupted at rump; black, with yellow cross-bands; sides of neck yellow. 



C. oreviroHtria Cope. 



Head wedge-shaped; three or four scales on canthus rostralis; all, except 



the posterior one, deeper than long; dorsal crest interrupted at rump; 



black, with yellow and green cross-bands and speckles C. teres Harlan. 



Four canthal scales, the posterior longer than deep ; head elongate, wedge- 

 shaped; dorsal and caudal crests continuous at rump; tail compressed; 



green, with narrow black cross-bauds to belly C. completa Bocourt. 



III. Caudal whorls iuterrupted; each represented by a median dorsal spine and two 

 on each side at the base. 

 Tail depressed, shorter; dorsal crest widely interrupted at rump; pale brown, 

 with black cross-bands on anterior dorsal region.. C. quinquecarinata Gray. 



The genus Ctenosaura includes species of large size, which inhabit 

 the forests of the Central American region. In other parts of Neotro- 

 pica they are unknown. In the West Indian region their place is taken 

 by the genus Gyclura, while Iguana ranges almost tlie entire realm. 

 One species enters the extreme limit of Nearctica, at the southern part 

 of the Lower Californian Peninsula, and one occupies the Plateau to 

 southern Arizona. 



The species are powerful and active, and can make a good defense 

 when necessary by the use of their small sharp teeth and of their 

 spinous tail. This organ is armed with rings of spinous scales, which 

 are very acute, and which inflict considerable wounds when driven 

 against the naked surface of the skin. In the smallest species, the 

 C. quinquecarinata, the spines are especially large and are fewer in 

 number than the other species, the form approaching the allied genus, 

 Cacliryx Cope. In the latter, of which the species are also Central 

 American, the tail is abbreviated so as to be si)inous to the end. In 

 Ctenosaura the spines terminate a considerable distance cephalad of 

 the distal part of the long slender tail. 



These reptiles are valued as food by the natives of Central America, 

 where they, like other large tree lizards, are called Iguanas. 



CTENOSAURA HEMILOPHA Cope. 



Ctenosaura hemilopha Cope, Proc. Acad. Nat. Sci. Phila., 1863, p. 105. — Bou- 

 LENGER, Cat. Liz. Brit. Mus., 2d ed., 1885, p. 197.— Van Denburgh, Proc. 

 Cal. Acad. Sci., 1895, p. 88. 



Iguana (Cyclura) acanthura Blaina'ILLE, Nouv. Ann. Mus., lY, 1835, p. 288, pi. 

 XXIV, fig. 1 (not of Shaw). 



Cyclura acanthura Dumeril and Bibron, Erp. G<5n. IV, 1837, p. 222. 



Ctenosaura acanthura Bocourt, Miss. Sc. Mex. Rept., 1874, p. 138. 



Ctenosaura interrupta (DuGi:s) Bocourt, Le Naturaliste, II, 1882, p. 47. 



Breadth just anterior to the orbits equal to length from line connect- 

 ing those points to end of muzzle. Eostral plate twice as broad as 

 high, upper outline an arc. Seven premaxillary teeth; maxillaries (in 

 one specimen) 21, of which six are conic, the third longest, and very 

 few of the remainder more than tricuspid. 



