374 HYATT: GENEALOGY OF ACHATINELLID^E. 



Kauai is nearly as large as Oahu, the metropolis of the 

 Achatinellida, but has a much simpler topography. There is 

 one peak of 5000 feet in the center of the island and the 

 valleys radiate from this outwardly, whereas in Oahu there 

 are two ranges, the longest of which, the eastern range, cuts 

 across the track of the northeast trade winds, while the 

 shorter or western range is nearly parallel with this. The 

 highest peak in the former is to the northeast of Honolulu 

 and is 3175 feet, while the highest peak in the western range 

 is 4030 feet. 



The four islands next to Oahu geographically and faun- 

 ally, are a group by themselves, and can be treated as one ex- 

 cept in the minuter study of the distribution of species. 

 These are Molokai next to Oahu, Lanai and Maui, and the 

 small island of Kahoolawe apparently having no shells of 

 this family existing upon it. 



The areas of these islands are as follows : Molokai, 190 

 square miles; Maui, 620 square miles; Lanai, 100 square 

 miles, and Kahoolawe, 60 square miles, in all 970 square 

 miles. 



Hawaii, the extreme southeastern island, is the largest and 

 highest, and has the only active volcanoes in the chain. Its 

 area is 3950 square miles. The recent and active volcanoes 

 of Hawaii, the presence of extinct craters on other islands, 

 the steady progress in size from northwest to southeast and 

 the deeper valleys and more sharply set ridges and peaks of 

 the northwestern islands, all tend to confirm the conclusions 

 of geologists that the Hawaiian islands arose in succession 

 through volcanic action, and by upheaval out of the water 

 starting with either Niihau or Kauai; Hawaii being the 

 youngest and largest of the group. Kauai is very nearly as 

 large as Oahu, and Hawaii is much larger, and yet both of 

 these extremes of the chain have meagre faunas compared 

 with Oahu, and the other intermediate islands. 



This shows that there is as yet no correspondence between 

 the area or topography of each island and the abundance or 

 scarcity of Achatinellida. Baldwin expressly states that 

 Kauai is, apparently, extremely favorable for the develop- 



