Occasional Papers of the Museum of Zoology 99 



Distribution of species: Curagao; practically everj-where on 

 the limestone, and also invading the region of the older rocks. 

 Bonaire: as prevalent as on Curacao. Klein-Bonaire: eveiy- 

 where. Aruba : Perkietenboseh and Baranca Alto. Mainly on 

 brush and cacti a short distance above the ground, but also 

 on and under rocks. Very abundant in favorable localities; 

 as many as 150 per square meter counted. 2,737 adults col- 

 lected. 



Distribution of subspecies: Curagao; the southern portion, 

 north of Kaap Sint Marie and Landhuis Hato (at least) ; 

 mainly on limestone (Cl-13), but also narrowly invades the 

 region of the older rocks (Cb6, 10). 



Extreme variability appears to be a characteristic of this 

 genus. In order to obtain some statistical idea of the amount 

 and character of the variation in C. uva, the altitude, major 

 diameter (exclusive of aperture), and the number of whorls 

 were ascertained in all of the Curacao specimens collected. 

 These data indicate that the variation may be immediately 

 divided into two phases: the number of whorls and the dia- 

 meter of the shell. The former would seem to be simply a 

 function of the period of growth; while the latter expresses 

 actual variation in size (dwarfing or gigantism). The dia- 

 meter does not seem to be especially correlated with the num- 

 ber of whorls ; in other words, the larger shells do not appear 

 to develop more whorls, although this is not strictly true of 

 the extremes in size. Inside of each subspecies, on the other 

 hand, the altitude is very closely correlated with the number 

 of whorls (see Table XI). 



Table XII shows immediately that neither of these varia- 

 tions is geographical; colonies with low (or high) means occur 

 in widely separated places. The explanation is, I believe, 

 purely ecological. The size of the shells {i.e., the diameter) 

 appears to be directly dependent on the richness of the habitat. 

 Almost without exception, the lots, with a mean major diam- 

 eter of over 10 mm., occur in the most heavily wooded por- 

 tions of the limestone or central region; these places are 

 usually near the larger hills, which probably increase the rain- 



