XXXV111 HABITS AND STATIONS. 



tically complete destruction of primaeval forest on the lower 

 levels. 



The chief area of Achatinella is from the ridge down to 

 about the 1000 ft. contour on the southern or Kona slope. 

 The best published maps of Oahu give a wholly false idea of 

 the topography of the western half of the Main Range. The 

 fact is that the precipitation along the main mountain axis 

 has formed great amphitheatres along the lee side. The 

 ridges running westward or southwest from it are in part 

 broken down, lowered, and worn to knife-like crests. Several 

 miles further from the main axis, where erosion has been 

 less potent, the ridges broaden out and branch, so that to- 

 wards their lower ends there are more and wider high ridges 

 than further up. Far down, finally, they may be cultivated 

 on top. A map of this region, supplied by Mr. Spalding 

 from his note books, is given on page 277, in order that an 

 intelligent idea may be formed of the localities mentioned in 

 the text for the western species. 



In the Waianae range (see p. 341) the conditions are 

 similar. Though it rises to a greater elevation than the Main 

 range, it has also been more extensively eroded. Broad val- 

 leys, separated by knife-like or interrupted butresses, have 

 been carved out on the southern (ocean) side, heading for the 

 greater part in precipitous slopes, mostly inaccessible. There 

 is a narrow fringe of forest, with tree-snails in places, around 

 the heads of these valleys, but the major part of the slopes 

 themselves are almost or quite barren, and too steep to sup- 

 port forest. The valleys of the inland side of the range 

 head up so near those of the Ocean side in some places that 

 only a narrow, wall-like arete remains, as above the heads of 

 the Popouwela gulches. Standing on the wild-goat trail at 

 the summit, a stone dislodged on either side might bound 

 downward a thousand feet or more, so narrow is the ridge. At 

 Waianae Pass the range has been almost gnawed through. 

 Immediately west of this pass Mt. Kaala rises, the highest 

 point on Oahu huge, flat-topped, its summit drenched by 

 daily cloud or rain. West of Kaala the ridge narrows again. 

 At the northwestern end of the range, where the foothills ap- 



