76 AURICULELLA, OAHU. 



a matter of degree as between pulchra and the five species 

 following. Old specimens of auricula, montana, etc., have 

 an incipient and inconspicuous development of the " dupli- 

 cate " structure. 



1. A. DIAPHANA Smith. PL 27, figs. 1 to 6. 



''Shell sinistral, ovately conic, very thin, corneous, striped 

 with brown, obscurely encircled at the middle of the last 

 whorl by a brown band ; whorls 5^, slightly convex ; suture 

 simple; lip thin, slightly dilated; columella scarcely plicate, 

 sometimes reflexed, forming a small umbilical cleft, joined to 

 the lip by a thin callus; parietal lamella thin. Length 7, 

 diam. 4 mm." (Smith). 



Var. " Shell unicolorous ". (Sm.) 



Oahu: Olornana, Kailua, Palolo, Kalihi (Gulick), Makiki 

 (Gulick, Cooke, Pilsbry), Tantalus (Perkins, Cooke, Pilsbry), 

 Pauoa (Perkins, A. A. Heller). 



Auriculella diaphana SMITH, P. Z. S. Lond., 1873, p. 87, pi. 

 10, fig. 25. PFR., Mon. Hel. Viv., viii, p. 209. ANCEY, Bull. 

 Soc. Malac. France, vi, 1889, p. 219. SYKES, Fauna Hawai- 

 ieiisis, Moll., p. 376. 



" It is like Aur. tennis Smith, in structure, and like Aur. 

 auricula Fer. in form. The latter species, however, is usually 

 dextral, while this is almost always sinistral." (Smith.) 



A large series of about 600 specimens, agreeing closely with 

 the above description, was collected by the authors at the 

 head of Makiki Valley, and others around Tantalus, where 

 it is an abundant snail. All the specimens are remarkably 

 constant in form and texture, and all are sinistral. Twenty- 

 five examples taken at random were carefully measured and 

 have an average length and diameter of 7.05 x 3.96 mm. The 

 largest specimen was 7.7 x 4.0 mm., the smallest 6.6 x 3.7 mm., 

 and the mean variation from the average length was only 0.2 

 mm. 



The common color- varieties are: (a) unicolorous dark red- 

 dish brown ; ( 6 ) corneous with broad indistinct stripes of a 

 slightly brownish corneous; (c) corneous with a narrow light 

 colored band bordered above and below by narrow dark 



