414 PROCEEDINGS OF THE ACADEMY OF [1896. 



and continued to do so until they completed their shells, or were 

 forced, immature, to go into hibernation. Completing their shells 

 under pressure and affected by the environment the thickening of 

 the aperture was more or less irregularly deposited, and the excess 

 of shell matter appears in the form of tubercles or lumps of callus 

 disposed about the aperture. As might be expected, so far as we 

 know the situs of the various species, these peculiar deformations 

 occur chiefly among the species of the dry zone below or the grassy 

 zone above, the conditions of the intermediate wooded zone are 

 probably more uniform, or, perhaps, species living on the ground or 

 on low herbage are more likely to be affected by alkaline efflores- 

 cences than those which live at a greater height on trees and shrubs. 



If these views are correct, we should expect to find analogous 

 effects produced on similar mollusks in similar situations throughout 

 the world. They should be produced without reference to the line of 

 descent of the species, that is, species of the European Buliminus or 

 the African Achatina should in analogous situations exhibit practi- 

 cally the same sort of deformation as has just been described in spe- 

 cies of Bulimulus isolated on the Galapagos. Is this the case? 

 Analogous situations are not very numerous. Wanted, an island 

 habitat with volcanic rocks, a climate combining periodical dryness 

 with occasional wet mists and a regular rainy season. In the 

 Hawaiian Islands we have something of the sort, but, owing to their 

 larger size, there is a much more continuous flow of water in streams, 

 the climate is not so hot and the parallel is far from exact. The 

 island of Fernando de Noronha has been said to have a remarkable 

 resemblance to the Galapagos, and so did St. Helena before it was 

 deforested. A glance at the fauna will be of interest. 



The island of Fernando de Noronha like the Galapagos is volcanic, 

 with a soil formed by decomposition of the basalt, and is well sup- 

 plied with vegetation and water. Smith says of the mollusk fauna^ 

 " Of the land shells two are well known West Indian species, one 

 has been recorded from Brazil, Peru and the island of Opara, and 

 the remaining four, up to the present, appear to be peculiar to the 

 island. One of these, however, Bulimus Ramagei suggests a faunis- 

 tic similarity to Brazil, as the section of Bulimus to which it belongs 

 (Tomigerus) with one exception occurs only in that country." 



The species are as follows according to Smith : 



1. Helix (Polygyratia) quinquelirata Smith. 



5 Journ. Linn. Soc. Zool., Vol. XX, p. 484, 1890. 



