OF CONCHOLOGY. 157 



supra plano-depresso ; et angulato ; callus basalis elevatus, 

 tenuissime granulosus ; labro tenui, ad angulam vix emarginato ; 

 apertura late lunaris ; rufescente aut flavescente. 



Dimensions. — Diam. 3, alt. 1J mill. 



Hab. — Insl. Atiu. 



Shell rather thin, orbicular, obliquely finely striate, spire 

 elevated ; suture well impressed ; whorls 4, convex, the last 

 flatly depressed above and angulate ; basal callous elevated, 

 finely granulose ; lip thin, slightly emarginate at the angulation ; 

 aperture broadly lunate ; reddish or yellowish. 



Remarks. — This species is one of the smallest of the genus. 

 It has several peculiarities by which it may be recognized. The 

 depression of the last whorl, more especially near the lip, which 

 is emarginate at the angulation produced and the fine granules 

 on the basal callosity. All the land shells inhabiting the above 

 group of Islands, with the exception of one species of Partula, 

 are the smallest in Polynesia. Three species of Omphalotrojris, 

 affinis, Pse., ochrostoma, Pse., scalar if or mis ^ Pse., are the 

 smallest of the genus. Helix (Pithi/s) rotellina, Pse., is one of 

 the smallest of known Helices, and the species of the Cyclos- 

 tomoid genus described below are but 2J mill, in diameter. 



Helicina rugulosa, Pse. Plate 12, fig. 11. 



Description. — T. tenuiscula, depressa, orbicularis, oblique for- 

 titer et rude striata ; spira vix elevata ; sutura bene impressa ; 

 anfr. 3 J, convexis, ultimo rotundo-angulato ad peripheriam ; 

 basi planiuscula ; callus basalis tenui, depressus ; labro vix 

 incrassato ; omnino flavescente aut rufescente. 



Dimensions. — Diam 3|, alt. 2 mill. 



Hab. — Insl. Tahaa. 



Shell rather thin, depressed, orbicular, obliquely strongly and 

 rudely striate ; spire slightly elevated ; suture well impressed ; 

 whorls 3|, convex, the last roundly angulate at the periphery ; 

 base rather flat, basal callosity thin, depressed, lip thickened ; 

 color wholly yellowish or slightly reddish. 



Genus DIADBMA, Pease. 



Description. — T. globoso-turbinata, umbilicata, perist. continu- 

 um, rectum, liberum aut vix adnatum, simplex, subcirculare. 



Operculum, subcartilagineum, elevatum, spiraliter lamellatum, 

 intus concavum, basi late reflexum. 



Remarks. — The above genus is founded on a shell we referred 



