PARTULA, RAIATEA AND TAHAA. 223 



of imperforata. Although I give Garrett's description above. 

 I am convinced that no study of descriptions or of the type 

 specimens, which I have before me, would enable one to 

 separate a series of the two forms if mixed. The distinc- 

 tion is based chiefly on geographic distribution but also 

 to some extent on the diverse variations of the two forms. 

 Pale specimens of virginea usually have the apex purple- 

 tipped (not pink, as in raiatensis) ; but the darker shells have 

 the embryonic whorls white. The only closely related or 

 similar shell on Tahaa is P. planilabrum, which belongs to 

 the fab a series. 



The figures are from Garrett's type lot, no. 59474 A. N. 

 S. P. 



Group of P. liebe. 



In this group of rather small forms the spiral striae are 

 usually somewhat better developed than in most other Rai- 

 atean species. The relations of the main forms may be ex- 

 pressed diagrammatically, thus: 

 thalia garretti 



I 



umbilicata 



hebe 



rustica crassilabris 



27. P. HEBE Pfeiffer. PI. 21, figs. 1, 2, 3. 



Shell perforate, globose-conic, thin, under the lens most 

 minutely decussate, hyaline. Spire short, conic, acute. 

 Whorls 4%, flat, the last longer than the spire, globose. 

 Columella short, subplicate; aperture wide, almost semicircu- 

 lar, having a deep-seated tooth-like callus on the belly of the 

 penult whorl. Peristome white-calloused within, narrowly 

 expanded throughout. Length 16, diam. 9, aperture 7 x 5% 

 mm. inside. (Pfr.). 



Raiatea: "The specific centre of the type of this small 

 white species is in the large valley of Faaloa, on the eastern 

 coast of Raiatea, where it is found in great profusion on the 

 foliage of bushes. From this central point it has migrated 



