80 THE REPTILES OF THE GALAPAGOS ISLANDS. 



there are others from Albemarle, Charles, Duncan and 

 Jervis islands. All may he placed in a single species, in 

 which it seems possible, however, to distinguish three va- 

 rieties : first, the typical form of the species, A. cristatus, 

 with the young profusely mottled with whitish, greenish and 

 olive and the old reddish, mottled, and clouded with darker 

 on the sides and usually with a black blotch between the 

 shoulders (from Albemarle, Biudloe, Charles and Jervis) ; 

 second, A. a(er, the large black form, from Duncan, which 

 exhibits, in large specimens, little or none of the russet 

 color or the mottling ; and, third, A. nanus, a small black 

 form from Tower island, a form that does not appear to 

 reach half the size of that from Duncan, and which becomes 

 nearly uniform black at a size that in A. cristatus has more 

 of green and olive than brown. The smallest specimen of 

 A. nanus is five inches in length of body and seven and 

 one-fourth in length of tail ; the largest has a body eight 

 inches long and a tail twelve and a half. Two specimens 

 of A. ater were secured by Professor Agassiz, on the Al- 

 batross, from Duncan. The larger is fourteen inches in 

 body and eighteen and a half in tail. The color distin- 

 guishes them at once from A. cristatus. Of the latter those 

 from Charles appear to have more of the lighter colors in 

 the young, but in the old there is little difference to be 

 detected between the several localities. The smallest spec- 

 imen, from Albemarle, measures four and a half inches 

 in body and five and three-fourths inches in tail. It has 

 eight or nine transverse bands, or series of lighter spots, 

 from nape to base of tail, is mottled with lighter on flanks, 

 and is coarsely puncticulate with brown under throat and 

 breast. On the small ones the tubercles of the head are 

 light colored, and spots of the same color form a sort of 

 rosette on the nape. The tubercles of the forehead are 

 flat or convex scales at first, later they become carinate 



