176 PARTULA, SOCIETY ISLANDS. 



simple; aperture ample, peristome expanded, not thick- 

 ened. Section Leptopartula, species 7 and 8. 

 II. Shell composed of more than 4.y 2 whorls, usually solid, 

 with opaque coloring, but sometimes white ; lip thickened 

 within. Section Partula, species 9 to 50. 

 Up to this time we owe our knowledge of the distribution 

 and variation of Society Island Partulae to Andrew Garrett, 

 whose residence at Tahiti gave him unusual facilities for their 

 study. In the following account I have quoted largely from 

 his writings and except in a few cases, have accepted his esti- 

 mate of the rank of the several species and races. In a case 

 like this, where races in all degrees of differentiation abound, 

 the rank to be assigned to any given race is, in the last re- 

 sort, a matter of opinion. The criterion of intergradation is 

 often difficult of application, as where the racial divergence 

 is expressed chiefly in slightly different tendencies of varia- 

 tion. In Raiatea and Tahaa especially, there seems to be a 

 good deal of intergradation between the races and so-called 

 species. 



Section LEPTOPARTULA n. sect. 



Echo HARTMAN, Cat. Gen. Partula, 1881, p. 11 ; not of 

 Selys. 1853. 



The shell is ovate with short spire, and composed of few 

 (4 to 4!/2) whorls; very thin, fragile and somewhat trans- 

 parent, pale; aperture large, ovate; lip expanded, not thick- 

 ened. Type P. arguta. 



Two species, the most fragile of the genus, compose this sec- 

 tion, which is confined to Huaheine and Raiatea, 



7. P. ARGUTA (Pease). PL 24, figs. 14, 15. 



The shell is narrowly but deeply perforate, short, ovate, 

 extremely thin, fragile, corneous usually with a faint buff tint, 

 and imperfectly transparent. Surface rather glossy, marked 

 with weak growth-lines and microscopic incised spiral stride 

 which are weak on the last whorl but distinct and close on 

 the spire. The spire is very short, conic; whorls 4, convex, 

 the last evenly convex, globose. The aperture is somewhat 



