PARTULINA. 361 



more pyramidal shape with broad white lip-border and white 

 columella, while in redfieldi the last whorl of the shell is larger 

 and the lip and columella are dark. P. dwightii is a western, 

 P. redfieldi an eastern species. Puukolekole, where we 

 collected a couple of hundred in a colony on the eastern 

 side, is about the eastern limit of dwightii. In this colony we 

 found a few real redfieldi (pi. 26, figs. 5, 5a), forming about 

 16 per cent of the whole. The two species overlap in this dis- 

 trict, and it can hardly be doubted that they form hybrid colo- 

 nies, segregating into the brown- and the white-lipped forms. 



Westward, P. dwightii is not known farther than Makaku- 

 paia, to my knowledge ; but it formerly extended as far as the 

 summit of Manuna Loa, and Moomomi on the north coast, in 

 a slightly modified form, described below. 



The Puukolekole colony is illustrated in pi. 26, figs. 5 to 5/. 

 It is clear that in this colony the forms called compta Pse. and 

 concomitans Hyatt are mere color-mutants, and in no sense 

 races. The embryos removed from these shells show that 

 several patterns are often the progeny of one parent. 



Partulina dwightii, color-form concomitans, has been erron- 

 eously referred to as Achatinella macrodon by Perkins, Fauna 

 Hawaiiensis I, pt. vi, p. Ixvi, 1913. 



Var. mucida Baldwin. Page 34. Typical mucida occurs 

 low down in Kamalo (Thaanum), and also in the type locality, 

 Makakupaia below Puu Kaeha. It is merely a small form or 

 race of dwightii. P. macrodon Borch. is not a variety but only 

 a color-mutant occurring with mucida. 



P. dwightii occidentals P. & C., n. v. PL 26, fig. 6. 



Smaller than dwightii, wider than mucida, aperture shorter, 

 the lip less prolonged basally. Length 20.5, diam. 12.6, length 

 of aperture 9.5 mm. 



Sand dunes of Moomomi (on the north coast almost due 

 north of Mauna Loa) ; also summit of Mauna Loa, under 

 stones. Cooke and Pilsbry, 1913. 



This Pleistocene variety shows that one time tree snails ex- 

 tended almost to the western end of Molokai. A single frag- 



