AMASTRA, MOLOKAI. 249 



opinion the errors of identification are somewhat numerous, 

 because in the present state of the subject, certainty is un- 

 attainable in dealing with Molokaian Amastras and Lami- 

 nellas. 



Most of the cases cited by Borcherding of Achatiuellidce oc- 

 curring on two or more islands are either based on faulty 

 data, or in some cases rest upon a wider conception of " spe- 

 cies ' ' than the authors have used in this work. So far as we 

 know, Amastra hutchinsonii is the only Molokaian species of 

 this genus which is common to another island (Mam), though 

 several forms of the assimilis group of eastern Molokai and 

 Maui are closely related. 



Key to Amastra of Molokai. 



I. Shell deeply umbilicate, small (length about 9 to 11 mm.), 

 brown. A. umbilicata, no. 65. 



II. Shell rimate or imperforate. 

 a. Shell sinistral. 



&. Small, 11.5x5.5 mm., witii weak sculpture. 



A. perversa, no. 82. 



ft 1 . Larger, length 15 to 25 mm.; roughly sculptured. 



A. hutchinsonii, no. 89. 

 a 1 . Shell dextral. 



&. Embryonic whorls finely striate. 



c. Small, length 9 to 12 mm.; banded; no an- 

 gularly striped cuticle. 



d. Moderately solid, brown with a subsutural 



whitish band. A. petricola, no. 66. 



d 1 . Very solid, lip, columella and parietal 



callus thick; fossil. A. abavus, no. 67. 



c 1 . Larger, length over 15 mm. 



d. Cuticle dense, black, variegated on spire ; 

 dull red within the lip ; 16 to 18x9 mm. 



A. humilis, no. 68. 



d 1 . Striation very weak; closely speckled and 

 ragged-striped on a cream or pale fleshy 

 ground; lip white within. 



