406 



PROCEEDINGS OF THE ACADEMY OF 



[1896. 



of a person sufficiently expert to recognize the species when col- 

 lected, and to collect with judgment in all the zones. Dead speci- 

 mens are so easily carried down hill by wind or temporary rills of 

 water in the rainy season, or transported and dropped by birds in 

 places which they did not originally inhabit, that no weight can be 

 gfven to the place of their occurrence in such a discussion as this. 

 In regard to some of the species, no information is available ; some 

 of the others have been collected in a dead condition from the dry 

 zone below 800 feet, which are known to live in the wooded zone 

 above, hence these may be eliminated from the local population of 

 the dry zone. Making such eliminations, the known population of 

 the dry, the wooded and the grassy upper plateau regions, respec- 

 tively, are as follows : 



Bulimulus Wolfi. 

 B. rugulosus. 

 B. planosjnra. 

 B. ustulatus. 

 B. calvus. 



DRY ZONE. 



B. eschariferus and var. ventrosus. 

 B. galapaganus. 

 B. perspectivus. 

 Pupa elausa. 

 P. mimita. 



WOODED ZONE. 



Bulimulus nux 

 and varieties. 

 B. achatellinus. 

 B. jacobi. 

 B. acutus. 

 B. nucula. 

 B. amastroides. 



Bulimulus olla. 



B. cuHus. 



B. unifasciatus. 



B. Bauri. 



B. canaliferus. 



Conulus galapaganus. 

 Succinea Bettii. 

 S. brevior. 

 S. producta. 



B. chemnitzioides. Leptinaria chathamensis. 



B. Kabeli. 



Vitrea chathamensis. 



Helieina nesiotica. 



GRASSY ZONE. 



B. Simrothi. 



It is not at all improbable that some of the species of the wooded 

 zone extend downward into the dry or partially dry zone, and that 

 the singular variations observed in some of the species may be due 

 to the direct action of the differing conditions in which they, respec- 

 tively, exist. Making allowance for this, the chief distinction which 

 presents itself between the species of the dry zone and those of the 

 wooded zone, is that the Bulimuli of the dry region show a tendency; — 

 1, To a pupiform shape (such as might facilitate their entry into 

 narrow crevices beneath the lava blocks) ; 2. To reddish-brown col- 



