PABTULINA, SECTION BALDWINIA. 93 



lated to the shells -of Molokai and Maui than to those of the 

 more distant islands of the group farther north. It is highly 

 probable, indeed, that the latter island furnished the parent 

 forms, the channel separating the two islands being less than 

 twenty miles wide. As species are reckoned in this group, 

 the Hawaiian forms are distinct* enough from any Maui shells, 

 although the A. physa of Hawaii is rather closely related to 

 the P. grisea of Maui, both in form and coloration, and the 

 latter may have been the parent form, or at least descended 

 from a common ancestor. 



* The color of the typical and prevailing form of A. hor- 

 neri is white with a broad zone of brown around the periph- 

 ery, thence visible to the apex as a faint line above the suture. 

 There is also, as noted by Mr. Baldwin, a pure white form of 

 this species, and a third variety with only the apical whorls 

 brown banded. To these is to be added a fourth color- variety, 

 not previously noted, which is white save that the apex, for 

 a varying distance, is tinged with brown. Of the four color 

 forms, only the typical shell and the white variety are at all 

 common; the other two are rare. 



' There is some evidence to prove that formerly, even so 

 late as ten years ago, the brown-whorled form was much 

 more abundant than it is now, and many dead shells have been 

 found on the heights between Waipio and Waimanu valleys 

 where the living shells are very rare indeed (some living ones 

 have been found by Mr. Thaanum) . 



" It is to be noted particularly that all the above forms of 

 horneri occur in the same locality and on the same species of 

 trees, but individual trees are never occupied by two forms. 

 Moreover, with the possible exception of the banded form and 

 the pure white one, the color varieties appear not to inter- 

 grade. 



' ' As regards shape the four forms do not seem to differ ap- 

 preciably. Roughly speaking there may be said to be a large 

 and a small form of each of the four, but it is of interest to 

 note that, while the individuals of each form intergrade in 

 size, large and small forms do not live upon the same tree. 

 The adult individuals on a tree are either all large or all 



