ART. 12 EEVISION OF LIZARDS OF GENUS CTENOSAUEA BAILEY 7 



the young as a rule being more or less greenish, while the adults 

 become darker and often marked with black or brown. In very old 

 specimens the color oftentimes becomes a reddish or rusty brown or 

 even black. Both young and old of some species have spots and 

 stripes. The great number of synonyms found in this genus are prob- 

 ably due, at least in part, to the lack of a proper consideration of 

 these variatioMs. 



At the beginning of this study it was thought that possibly there 

 were some osteological characters upon which this and nearly related 

 genera might be definitely separated. However, a careful examina- 

 tion of Iguana, Ctenosaura, and Cyclura shows only slight differences 

 in the skull, and even these differences can not possibly be called 

 generic differences. As a matter of fact, the only dift'erences are to 

 be found in the general outline of the skull, and these are no greater 

 between genera than between species of the same genus. The skull 

 of Iguana and Cyclura are typically iguaniform in size and shape, 

 while in Ctenosaura pectinata and similis the skull is slightly elongated 

 and flattened dorso-ventrally. Yet in hrevirostris the rostrum, as 

 indicated by the specific name, is short; the skull is not flattened 

 but would pass for a true Iguana. It is impossible to distinguish 

 between the genus Ctenosaura and its near allies by means of skeletal 

 characters. 



The early and most primitive forms of these lizards had very elon- 

 gated tails and bodies — the true reptilian type, so to speak. Thus 

 acanthura, supposedly the most primitive of the living forms of the 

 genus, has a very long tail. It appears that as this form migrated 

 the tail has tended to become shorter. It is interesting to note that 

 along with the reduction in the length of the tail there is a corre- 

 sponding increase in the size of the caudal spines. Also the species 

 possessing the largest spines have the smallest bodies. The large 

 spines on the tail will probably help to protect the species from 

 enemies, while the small size of the body renders it undesirable as 

 food for man, the most relentless enemy of these large lizards. 



Genus CTENOSAURA Wiegmann 



Type. — Ctenosaura cycluroides Wiegmann, 1828, Oken's Isis, p. 371 

 {Ctenosaura acanthura). 



Ctenosaura Wiegmann, 1828, Oken's Isis, p. 371. — Gray, 1845, Cat. Lizards Brit. 

 Mus., p. 191. — BocouRT, 1870, Miss. Sci. Mex., vol. 3, Reptiles, p. 136.— Cope, 

 1885, Proc. Acad. Nat. Sci. Philadelphia, vol. 23, p. 262. — Boulenger, 1885, 

 Cat. Lizards Brit. Mus., vol. 2, p. 195.— Cope, 1886, Proc. Amer. Philos. Soc, 

 vol. 23, p. 216; 1887, Bull. 32, U. S. Nat. Mus., p. 33.— Gunther, 1890, Biol 

 Centr. Amer., Reptiles, Batrachia, p. 50. — -Cope, 1900, Report U. S. Nat. Mus 

 for 1898, p. 237.— Brown, 1904, Proc. Acad. Nat. Sci. Philadelphia, vol. 56, p 

 468.— DiTMARs, 1907, Reptile Book, p. 106; 1910, Reptiles of the World, pp 

 140-141.— Barbour, 1916, Bull. Mus. Comp. Zool. (Part), vol. 60, No. 4, p 



