14 THE NAUTILCS. 



for the time ignoring the numerous " varieties " or subspecies, Oahu 

 has 28 species of Amastra in the Main Range, 15 in the Waianae 

 Range. Such a proportion seems natural in view of the comparative 

 magnitude of the two ranges. The species fall naturally into five 

 series, which may be called the umhilicata series, the undata, the 

 cornea, the injiata and the spirizona series. 



The undata series belongs to the Main Range, especially its 

 eastern half, where it is developed in a great variety of forms. Two 

 of the fourteen species have been found in the Waianae range, one 

 of them, Amastra albolabris unchanged, and another represented 

 in the Waianae Range by two varieties of A. reticulata, not very 

 different from the presumably parent form of the species in the main 

 range. 



The injiata series is also wide-spread in the Main Range, but one 

 variable species, Amastra rubens, has several varieties in the Waianae 

 range, and one Waianae species, A. porcus, is distinct from any in 

 the Main range, though probably related to A. tristis. 



The small cornea series has three species, one of them fossil, in 

 the Waianae Range, and one very rare species, A. (emulator Pils., 

 has recently been turned up in the Main Range. 



The spirizona series comprises seven species in the Waianae 

 Range. Amastra porphyrea Nc. is found also in the Main Range, 

 where there is moreover a distinct but related species, A. porphyros- 

 toma. A. spirizona of Waianae has several varieties in the Main 

 Range — nigrolahris, chlorotica — and one derivative species, A. turri- 

 tella. The last is the only form which has extended into the eastern 

 end of the Main Range. 



In dealing with groups of closely related species in limited areas 

 there cannot be much chance of error in holding that the region of 

 greatest variety and abundance of strictly localized specific forms has 

 been the center of differentiation of those forms. If so, it may be 

 seen that the undata and injlnta series had their rise in the 

 Main Range and the cornea and spirizona series in the Waianae 

 Range. 



To evolve so large a variety of species, many of them strongly 

 individualized, the two ranges must have existed as separate tracts 

 for a long time. It favors this view that fossil forms are found in 

 both ranges. Whether the separation was by water, or by a land 

 surface unfavorable to forest-snails, we have at present no means of 



