1895.] NATURAL SCIENCES OF PHILADELPHIA. 227 



wit hiu ; peristome acute, very lightly thickened within, expanded, 

 columellar margin reflexed over the small perforation, margined 

 with light brown on both face and the reverse ; columella very 

 slightly developed, plain and smooth. 



Length, 14 ; diam. 65 mm. 



Habitat, Halawa, Island of Molokai. 



Animal when extended in motion as long as the shell. Mantle 

 slate color, margined with brown. Foot light slate, studded on the 

 sides and head above with spots of deeper shade. Tentacles short 

 and slender, dark slate. 



The nearest allied species is A. sulcata Pfr., from which it may 

 be distinguished by its smaller size and more acute keels ; the 

 animals also differ and the habitats are widely separated. 



Section LAMINELLA Pfeiffer. 

 Laminella helvina, a. sp. PI. XI, fig. 30. 



Shell sinistral, imperforate or subperforate, sometimes narrowly 

 and deeply perforated, rather thin, elougately conical, apex rather 

 acute; surface scarcely shining, covered with very fine incremental 

 stria; ; nuclear whorls smooth. Color uniform light or dingy yellow, 

 with a few black markings on the upper whorls. ^Vhorls 6£, 

 lightly margined above, convex ; suture deeply impressed. Aper- 

 ture a little oblique, oval, white, with the tint of the outside ; peri- 

 stome simple, thin, margins connected by a thin, orange-yellow 

 callus; columella biplicate, the terminal plication a thin, oblique 

 lamellar plait, the inner one less prominent, tortuous, of an orange 

 yellow color. * 



Length, 18; diam. 10 mm. 



Habitat, Ohia valley, near Kaluaaha, Island of Molokai. 



Animal extended in motion as long as the shell. Mantle and 

 foot above and below very light brown. Tentacles dark slate, with 

 a sprinkling of slate on the sides of the foot. Posterior portion 

 of foot very tapering and thickly studded with minute red spots. 

 A remarkably prolific species ; 4 or 5 embryonic shells in successive 

 stages of growth often observed in the oviducts. A jaw is present 

 and the dentition is the same as that of the Amastra species. The 

 tooth formula of this species is 32.1.32 x 108 = 7,020. The central 

 tooth is a little wider than usual. (Prof. Gwatkiu.) 



This shell differs from all its congeners in its strongly biplicate 

 17 



