618 REPOKT OF NATIONAL MUSEUM, 1902. 



AMEIVA ALBOGUTTATA" Boulenger. 



1896. — Ameiva alboguttata Boulenger, Jahresber. Naturw. Ver. Magdeburg, 

 1894-1896, p. 112 (type locality, Mona Island; types in Mus. Mag- 

 deburg). — Meerwarth, Mitth. Naturh. Mus. Hamburg, XVIII, 1901, 

 p. 32, pi. ii, figs. 6-8 (Mona Island). 



This form is so much like Ameiva exul, from Porto Rico proper, 

 that a detailed description is unnecessary. It will suffice to indicate 

 in what respect the Mona Island specimens differ from the typical 

 species. 



The main difference seems to be one of coloration. Judging from 

 the alcoholic specimens, the Mona form is considerably paler than 

 those from Porto Rico proper. The white dots, as a rule, are more 

 numerous and extend farther forward on the back to between the 

 shoulders or slightly beyond, and it is probable that these spots do 

 not disappear with age, at least to the same extent as in the old 

 A. exul. There are young specimens of the latter, however, which 

 are fully as spotted as A. alboguttata, thus, for instance, Nos. 25665 and 

 25667, from San Juan, Porto Rico. In the young A. alboguttata 

 there is also present a more or less continuous white line between 

 axilla and groin, but this line disappears entirely in older specimens. 

 It is only indicated in a few young A. exul. 



In spite of the great variation in the size of the scales on the tail it 

 seems possible to establish an average difference between the two forms. 

 In 31 specimens of A. exul in which the scales in the fifteenth tail seg- 

 ment from the base were counted the number varied between 38 and 

 54, considerably more than one-half having 44 to 48 scales, the average 

 being 45.3. In the 7 specimens of A. alboguttata at hand the scales in 

 the fifteenth segment of the tail from its base numbered from 33 to 38, 

 the average being 34.4. 



The gular scales are exceedingly variable. As in typical A. exul 

 there is a median enlarged group, but it is not equally conspicuous in 

 all specimens. Sometimes it is fairly well defined, as in No. 29368; in 

 others the difference between these median scales and the adjacent 

 ones on both sides is so slight that they seem to form a band of nearly 

 equal scales across the throat, as in No. 29369; while in others again 

 the decrease in size of the scales from the median ones is so gradual in 

 all directions that no specially differentiated group can be made out. 

 Whatever difference there is in the covering of the throat in the two 

 forms seems due to the scales surrounding the median group being on 

 the whole slightly larger in A. alboguttata than in A. exul. The 

 difference is one of slight degree, not of kind. 



It seems as if in A. exul the inner row of enlarged tibials averages 

 somewhat larger. In some of the Mona specimens this row is very 



« White-spotted. 



