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PROCEEDINGS OF THE NATIONAL MUSEUM 



the smaller islands always been going on at the same rate. Seen in 

 that light rehderi and annae might be links in such a course of devel- 

 opment in which annae would represent the more specialized phase. 



Genus PHAEDUSA Adams 



PHAEDUSA (EUPHAEDUSA) ACULUS ANGKANENSIS, new subspecies 



Figure 53 



Shell small and less slender than is usually the case in aculus, the 

 lateral outlines being rather straight or slightly convex; thin, semi- 

 transparent, greenish or yellowish, glossy. Whorls fewer than usual, 

 81/2 to 9, very w^eakly striated, nearly smooth, even on the back of 

 the last whorl. 



Figure 53.— Phaedusa {Euphaedusa) aculus angkanensis, new subspecies: a, Ventral side 

 of holotype; b, right side of holotype. 



Aperture wide, nearly quadrangular with rounded angles. Peri- 

 stome whitish, thin, scarcely reflexed. 



Superior lamella widely separated from the spiral lamella, which 

 extends inward to the middle of the ventral side, not so far as the 

 inferior lamella and the subcolumellar lamella. 



Inferior lamella curving spirally inward ; the outer margin nearly 

 horizontal, forming with the columella, which is well visible in an 

 oblique view, a forklike structure such as is found in several varieties 

 of aculus., for instance, in insularis Heude. 



Principal plica from ventrolateral right to dorsal. Below it, later- 

 ally, there are 3 to 6 nearly parallel palatal plicae, as in other multi- 

 plicated forms of aculus. 



