92 HELLER 



The local variation is slight and so mixed with individual varia- 

 tion that it is difficult to define. With only our scanty material for 

 comparison — eighteen specimens representing eight islands — we have 

 not been able to detect any insular varieties nor would our observations 

 in the field lead us to infer that any well marked forms exist. 



The proportions are practically the same in all the specimens. The 

 largest specimens occur at Iguana Cove, where some attain a length 

 of four feet. Nowhere else do they attain these dimensions. On 

 Culpepper, Wenman and Tower they appear to average smaller than 

 on any of the other islands. 



The Duncan variety which has been described as uniform black 

 above has received the name ater. Our only specimen from Duncan, 

 an adult female, is no darker in coloration than specimens from other 

 islands, being blotched with greenish on the dorsum and mottled with 

 brownish on the sides. Those observed on the island were not notice- 

 ably darker than those seen on other islands. 



A single young specimen of the variety called nanus from Tower 

 Island is in the collection. The individuals observed at Tower ap- 

 peared somewhat smaller and darker, on an average, than those from 

 other islands but exceptions in size were not rare. 



Hood Island possesses the lightest forms. Two specimens in the 

 collection have the dorsum covered by a few large confluent light 

 greenish blotches, the head blackish and the sides and limbs mottled 

 with black and brown in about equal proportions. Nearly all the 

 specimens seen were remarkably light-colored and this coloration is 

 attained in this locality at an early age. 



The specimens taken on Culpepper and Wenman, though separated 

 in habitat from the others by a considerable expanse of ocean, are not 

 appreciably different. They average smaller, with less convexity to the 

 plates on the top of the head and snout and with smoother dorsal scales. 

 The green blotches are entirely lacking on the dorsum the upper parts 

 being black, spotted and mottled with brown. Some specimens, how- 

 ever, from the Seymour Islands duplicate these in coloration. 



Occasional migration at rare intervals probably occurs between all 

 the islands which keeps the stock apparently the same. 



Genus Dromicus Bibron. 

 Droviicus Bibron, in R. de la Sagra Hist. Cuba Erp., p. 221, 1843 (part). 



Range. — West Indies and west coast of South America from 

 Peru to Chile. Galapagos Archipelago (a single species and sub- 

 species). ♦ 



