140 bulletin: museum of comparative zoology. 



GENERAL CONSIDERATIONS. 



The members of the genus Cyelura form a small compact group of 

 species confined to the Greater Antillean district of the West Indian 

 region. Related to the Rock Iguanas (Ctenosaura) of the Central 

 American mainland they are nevertheless well set off from the latter 

 by the possession of the peculiar corneous combs or pectinations on 

 the hind toes. Except for this character common to all the West 

 Indian forms, some of these would appear more closely related to 

 some race of Ctenosaura than to another of the island species. On the 

 whole, it does not seem advisable to recognize the genus Metapoceras 

 for the so-called Rhinoceros Iguanas of Navassa, Haiti, and Mona, 

 since they are ob\aously but slightly advanced modifications of such 

 a type as the Jamaican Iguana, which is a true, and probably an- 

 cestral, Cyelura in every respect. The species in the Cayman 

 Islands is nearly related to the Cuban, and the number of forms 

 known from the Bahamas represent two groups of species, one showing 

 affinities with the Cuban, Cyelura macleayi. In the Bahamas, haeo- 

 lopha of Andros Island seems most like macleayi, with its neighbor, 

 inornata, hardly less similar; while nuehalis of Fortune, rileyi of 

 Watlings, and carinata from Turks Island form another well differ- 

 entiated group of races. The latter species has head-scales of a 

 simple and scarcely modified, one might, at first sight, say obviously 

 primitive nature. We imagine, however, that this condition has 

 been reached secondarily, the transition back through some of the 

 other species being clearly traceable. So that while the scales of the 

 head of earinata are of a very simple and undifferentiated character, 

 it is nevertheless extremely improbable, especially in view of its habi- 

 tat, that the species can be considered ancestral or anything more 

 than a reversion to the probably, or possibly, primitive condition for 

 Cyelura, and Ctenosaura, or their progenitors. It does not seem 

 wise to lay much stress upon the distribution of the species of Cyelura 

 as a basis for any zoographic deduction or sm-mise. We know but 

 little of the habits of the species, the whole group is fast disappearing 

 and will soon be wholly extinct, and even now we are able to character- 

 ize but eleven species, probably a comparatively small part of those 

 in existence even two hundred years ago. 



Early writers often mention Iguanas in the West Indies, and of 

 these some referred to the genus Iguana and some to Cyelura ; among 

 the latter was Catesby. This authority writing upon the Natural 



