LEPTACHATINA. 



Distribution, all of the islands except Niihau and Lanai, 

 (the fossils of which are unknown). With one exception, all 

 of the species are Pleistocene fossils. 



This is clearly a natural group, distinguished by a pecu- 

 liarity found in no other Achatinellid shell. It is of interest 

 to the zoogeographer because the group is common to the 

 Pleistocene deposits of most of the islands, and is thus an- 

 other proof that the island faunas of Pleistocene time were 

 more closely related than the recent faunas. Most other 

 groups of Leptachatina are not characteristic enough in struc- 

 ture to demonstrate the relationships of species from differ- 

 ent islands. 



The only living species of Angulidens are L. hyperodon of 

 Maui and L. microdon of Waianae. The following six species 

 are now known to belong to the group. 



L. FOSSILIS Cooke. Vol. XXI, p. 61. Kauai. 

 L. COOKEI Pilsbry. PI. 11, figs. 1, 2. 



The shell is perforate, ovate-conic, weakly marked with 

 growth-lines, or nearly smooth and glossy in the best pre- 

 served specimens. Apex small, obtuse. Spire straightly 

 conic above, convex below, the last whorl more or less notice- 

 ably cylindric, more flattened than the penultimate whorl; 

 the base is convex, compressed around the axial crevice. 

 Whorls 6!/2, slowly enlarging, the penultimate somewhat con- 

 vex, those above nearly flat. The suture is superficial ; in the 

 last third it ascends slightly, and at the aperture it is rather 

 abruptly, arcuately deflexed. The aperture is oblique, ovate, 

 contracted ; outer lip obtuse ; columellar lip reflected, thick- 

 ened on the face, and appressed above the narrow perforation, 

 continuous with a callous cord which bounds the rather thick 

 parietal callus, and terminates in an enlargement or tubercle 

 which is separated from the termination of the outer lip by a 

 narrow groove or posterior commissure of the aperture. The 

 columellar lamella is thin, broad and subhorizontal ; out- 

 wardly emerging to the edge of the columella. 



Length 10, diam. 5, aperture 4 mm. ; Qy 2 whorls. 



Length 9.5, diam. 4.9 mm. 



