38 DIVERGENCE UNDER THE SAME ENVIRONMENT. 



the most divergent species that have been chosen, but the most closely 

 related of those found on the different islands. 



In the case of arboreal species, the isolation between those inhab- 

 iting the forests of East Maui and those inhabiting the forest of 

 West Maui is almost as complete as if they inhabited separate islands ; 

 for the open grass land separating the two masses of forest-covered 

 mountains is as complete a barrier against direct migration as would 

 be a salt-water channel. There is, however, a somewhat better 

 chance of transportation by human agency across grass land than 

 across an equal width of water. 



Carelia is always dextral in form ; and I think it is terrestrial in its 

 habits. Amastra and Leptachatina, which are almost always found 

 on the ground, are with extremely rare exceptions dextral in form; 

 while of the arboreal genera, Newcombia and L,aminella are almost 

 always sinistral, and Auriculella, Apex, and Partulina have some spe- 

 cies constantly sinistral, others constantly dextral, and others that 

 assume either form. Achatinella and Bulimella (represented in Plates 

 II and III), are constantly arboreal in habits, and both dextral and 

 sinistral in the forms assumed. 



The following abbreviations are used in the "Notes" on the species 

 given in Plates I, II, and III. 



Per. = Ferussac; Gk. = Gulick; Migh. = Mighels; Nwc. = Newcomb; Pfr. = 

 Pfeiffer; Rv. = Reeve; Sm. Smith; Swn. = Swainson; D = dextral in form; 

 S = sinistral in form; D > S = the majority are dextral; S > D = the majority 



are sinistral ; S D = sinistral with the exception of about i in 500. 

 500 



NOTES ON THE SPECIES. 



FIG. i. Carelia cochlea (Rv.) D. From the island of Kauai. Examination of 

 the organs will probably place it with the Achatinellidae. 



FIG. 2. Amastra nucleola (Gould) D. From Waiole, Kauai. 



FIG. 3. Auriculella auricula (Fer.) D > S. This species, like others of this 

 genus, is found on the leaves of trees and shrubs. Its habitat is the eastern por- 

 tion of the forest region of the island of Oahu This specimen is from the valley 

 of Palolo. 



FIG. 4. Apex apicatus (Nwc.) D > S. From Wahiawa, Oahu. Also found in 

 Helemano and Ahonui. 



FIG. 5. Leptachatina fumosa (Nwc.) D. Found on the ground under dead 

 leaves, in damp forest regions from Nuuanu to Palolo, on the island of Oahu. This 

 specimen is from Palolo. 



FIG. 6. Laminella sanguinea (Nwc. j S. Found in Helemano and Wahiawa and 

 the intervening regions on the island of Oahu. This specimen is from Helemano. 



FIG. 7. Laminella citrina (Migh.) S. From the island of Molokai. 



FIG. 8. Laminella tetrao (Nwc.) S. From the island of Lanai. 



FIG. 9. Laminella -venusta (Migh.) S. From Lahaina, West Maui. 



FIG. 10. Laminella bulbosa (Gk.) S. From Kula, East Maui. 



FIG. ii. Partulina dubia (Nwc.) D. This is a rare species distributed over a 

 number of valleys of the island of Oahu from Waianae to Kalihi. This specimen 



