220 PARTULA, RAIATEA AND TAHAA. 



revealed its specific centre, and I took about eight 'hundred 

 specimens in various stages of growth, and many of the adults 

 were in a gravid condition. 



"It has been suggested that it may be a hybrid be- 

 tween faba and some other species. I only noticed 

 faba and garrettii in the lower part of the valley, and not in 

 the upper portion, which is the principal haunt of citrina. 

 Its uniform straw-yellow color, more slender form, smaller 

 perforation, more reflected columella, and more decided labial 

 tooth, and profounder emargination, will distinguish it from 

 the very variable faba. 



1 ' My largest examples are 25 mill, in length and 12 in dia- 

 meter. It is always of a straw-yellow color, rarely with faint 

 longitudinal darker strigations, and is either lemon-yellow 

 or light red at the apex. It is never spirally banded, and 

 the parietal wall is invariably edentate. The oblong white 

 aperture is, including the peristome, half the length of the 

 shell. The ivory-white lip is broadly expanded, planulate, 

 declivous, strongly labiated, slightly dentate and distinctly 

 emarginate above. The slightly gibbous columella is re- 

 flected over the small compressed perforation." 



26. P. IMPERFORATA 'Pease' Garrett. PI. 20, figs. 13, 14, 15. 



Shell imperforated or very narrowly compressly umbili- 

 cated, solid, oblong- conic, somewhat shining, with rather 

 smooth, irregular, incremental striae and closely set delicate 

 spiral incised lines, which are more or less evanescent on the 

 body-whorl. Color, pale straw-yellow, luteous, or fulvous, 

 often with a brownish apex. Spire conical, with subplanulate 

 outlines, about half the length of the shell ; suture sometimes 

 margined by a rugose white line; whorls 5-5^2? flatly convex, 

 the last one convex, or convexly rounded. Aperture sub- 

 vertical, oblong, obauriform, white, sides nearly parallel; 

 parietal wall with a more or less developed tubercular tooth; 

 peristome white, thick, moderately expanded, its face con- 

 cave, heavily labiated within, strongly contracted above, form- 

 ing a rather profound sinus, and generally subdentate next 

 to the emargination; columellar lip subnodose. 



