1920.] NATURAL SCIENCES OF PHILADELPHIA. 367 



Length 5, diameter 2.4 mm., largest specimen. 



Oahu: Honolulu, Mokapu Point and Paumalu (W. A. Bryan); 

 Haleiwa (Pilsbry). Maui: off Kaanapali in 60 feet. (Thaanum 

 and Langford). 



This species is smaller than Mnestia hizona (A. Adams), and does 

 not have the distinct bands of the typical form of that species; but 

 the relationship appears to be very intimate. 



The shore specimens are bleached quite white. 



Mnestia has been generally considered a subgenus of Cylichna. 

 Many authors consider the latter name to be a homonym of Cylich- 

 nus (Insecta), and moreover, Mnestia differs from Cylichna by its 

 well developed spiral sculptm'e; its soft parts are unknown. For 

 the present it appears best to treat the two groups as generically 

 distinct. 



AKERID.E. 

 HAMINCEA. 



Hamincea^ appears divisible into three sections by the structure 

 of the columella. These are defined in the following. 



Key to Hawaiian species of Hamincea. 



1. Columella deeply concave, the reflected columellar margin cres- 



centic, rather thick, its edge separated from the whorl by a 

 furrow. Section Haloa, new section, type H. crocata Pse 2 



Columella but slightly concave, the columellar edge free, narrow, 

 and but httle reflected, an umbilical crevice behind it. Shell 

 narrow (diameter less than half the length in our species); 

 sculptured with engraved spiral lines throughout. Subgenus 

 Liloa, new subg., type H. tomaculum Pils 4 



Columella concave, its reflected margin rather broad, thin, at 

 the edge closely appressed to the whorl. Section Hamincea 

 proper, type Bulla hydatis; not known to be represented in the 

 Hawaiian fauna. 



2. Apex perforate H. sandwichensis Sowb. 



Apex imperforate 3 



3. Oval; diameter two-thirds the length or less; yellowish when 



fresh; less than 14 mm. long H. crocata Pse. 



H. galha Pse. 



' Iredale has shown that the earliest speUing of "Haminea" was Haminaa. 

 Proc. Malac. Soc. Lond. XI, p. 172. 



