OF CONCHOLOGY. 229 



Diam., 4 mill. ; height, 2 mill. 



Habitat, Rarotonga Id., Cook's Isles. (Coll. Garrett and Phila. 

 Acad.) 



This species is confined to a single valley, where I found it 

 abundantly, under dead wood on the banks of a stream. Liv- 

 ing examples are uniform deep black. 



Pitys Youngi, Garrett. Plate i9, fig. 22. 



Shell umbilicate, discoid, thin, glossy, subpellucid, uniform 

 deep brown, plicately striated, striae crowded, oblique, curved, 

 rather finer beneath ; spire flatly convex ; suture channeled ; 

 whorls 4J, convex, rapidly increasing, last one convex beneath, 

 declivous above ; umbilicus large, perspective, freely exhibiting 

 the whorls, one-third the diameter of the shell ; aperture oblique, 

 wider than deep, orbicular-luniform ; peristome thin, simple, 

 margins united by a very thin parietal callous. 



Diam., 4 mill. ; height, 2 mill. 



Habitat, Rarotonga Id., Cook's Isles. (Coll. Garrett and Phila. 

 Acad.) 



A somewhat rare species, easily known by its wide open 

 umbilicus, few whorls, deep uniform brown color, and plicate 

 strise. On the ground in damp woods, and only noticed in a 

 single valley. 



Pitys tenuicostata, Garrett. Plate 19, fig. 23. 



Shell umbilicate, discoid, thin, pellucid, slightly shining, la- 

 minately ribbed, ribs small, thin, rather closely set, oblique, 

 slightly sinuous, continued on the base ; under the lens the inter- 

 stices, closely striated, uniform pale horn color ; spire flat; su- 

 ture deeply impressed ; whorls 4, flatly convex, rapidly increas- 

 ing, last one convex beneath, slightly flattened above ; umbilicus 

 large, perspective, freely showing the whorls, about one-third 

 the diameter of the shell'; aperture oblique, wider than deep, 

 ovate-luniform ; peristome thin, simple. 



Diam., 4J mill. ; height, 2 mill. 



Habitat, Rarotonga Id., Cook's Isles. (Coll. Garrett and Phila. 

 Acad.) 



A very pretty and somewhat rare species, having a wide range 

 on the island, and generally found on the ground on the sides of 

 ravines. 



