BaJhnus pallidior, which is pretty generally distributed through Lower Cali- 

 fornia, from Cape St. Lucas uortherlj', has also erroneously been credited to 

 San Diego in California j^roper. It is arboreal in its habits, at least during 

 the winter season, and frequents the Copaiva trees. It has been said to in- 

 habit South America, which is probably incorrect, and the locality " San Juan," 

 mentioned in " L. and F. W. Shells," on p. 195, where a good figure of this 

 species may be seen, should be San Jaanico, which is on the east side of the 

 peninsula, in latitude about 27^ N. 



The great importance of particularity in habitat will be at once perceived 

 when I state that there are no less than three other localities on the west coast 

 of America, north of the place cited, all of which are referred to in various 

 scientific works which have come under my observation, as " San Juan," and 

 there are jjerhaps as many more " San Juan's " south of that especially quoted 

 heri in, on the westerly coast of America, in the Central and South American 

 States. 



Attention is directed to the fact that the three species herein mentioned as 

 exhibiting extraordinary vitality, belong to geographical areas, which receive 

 only minimum raiufall, or which are, in simple language, nearly rainless 

 regions. 



Within such areas vegetation is exceedingly limited even in favorable sea- 

 sons, and the presence and growth of the annual plants is, of course, depend- 

 ent upon the rainfall; this last occurring infrequently makes the food supply 

 of land mollusks and other phytophagous or vegetable-eating animals exceed- 

 ingly precarious. 



It is highly probable that a careful investigation in this direction will lead 

 us to the conclusion that the land mollusks which inhabit arid areas have, 

 through selection, adaptation and evolution, become especially fitted for the 

 contingencies of their habitat, and possess a greater degree of vitality or abil- 

 ity to live without food than related forms in what may be considered more 

 favorable regions, and through and by reason of their long sleep or hiberna- 

 tion, more properh/ estivation, with its inactivity and consequent immunity from 

 any waste or exhaustion of vital strength, are enabled to maintain their hold 

 upon life when animals more highly organized would inevitablj' perish; and 

 we are furnished with an illustration, in the instances cited, how nature works 

 compensatively, when we institute a comparison with the opposite condition 

 of activity, and the food required to sustain it. 



