258 ACHATINELLA DIMORPHA. 



bands of a faint chamois tint. This form occurs with the 

 typical form (a) in Wahiawa, but without it in Ahonui, Hele- 

 mano and Kalaikoa. It is hardly to be distinguished from 

 bandless curt a, and approaches very close to rhodoraphe. 



The fact seems to be that the unicolored form of delta (b) 

 is a mutation of the curta-rhodoraphe stock which has rather 

 a wide distribution, and somewhere in Wahiawa district it 

 formed a hybrid colony with the streaked livida-curta stock; 

 pattern (a) of the heterogeneous lot called delta being 

 the result. Very likely the type colony of delta was limited 

 to a small area and is now extinct. 



26. A. DIMORPHA Gulick. PL 42, figs. 15 to 20 ; pi. 47. 



" Shell sinistral, sometimes dextral, imperf orate, turreted, 

 solid, shining, striated, white or yellow with a brown sutural 

 band [see below for bandless and for two- or three-banded 

 patterns] ; apex rather obtuse ; spire turreted ; suture mar- 

 ginate, moderately impressed, dark brown ; whorls 6, convex, 

 columellar fold central, white or rose, moderately developed; 

 aperture truncately ellipsoidal, white within ; peristome 

 slightly thickened within, with external margin unrenected, 

 arcuate, acute ; columellar margin dilated, adnate ; parietal 

 margin waiting. Length 18, breadth 9%, length of body- 

 whorl 11% mm. Average weight 4 grains. Habitat, Waimea, 

 Pupukea, Waialei and Kahuku, Oahu, J. T. G. ! Kaawa, 

 Oahu, J. S. Emerson' (Gulick). 



Oahu: northwestern ridges from Waimea to Kahuku; 

 Hauula and Kaaawa on the north side. 



Achatinella dimorpha GULICK, Ann. Lye. Nat. Hist, of 

 N. Y. vi, p. 236, pi. 8, f. 56. Achatinella albescens GULICK, 

 t. c., p. 237, pi. 8, f. 57; Evolution, Racial and Habitudinal, 

 p. 41, pi. 2, f. 2 (Pupukea). Achatinella zonata GULICK, t. c., 

 p. 238, pi. 8, f. 58; Evolution, etc., pi. 2, f. 1 (Pupukea). - 

 Achatinella contracta GULICK, t. c., p. 239, pi. 8, f. 59. Feb., 

 1858. 



A. dimorpha differs from A. curt a chiefly by its more 

 graceful lengthened contour, the last whorl being longer, less 

 inflated, and more slowly tapering below, whereas curta is 



