OPEAS, S.-E. ASIA. 161 



d'un partie de Flndo-Chine, p. 36; in Bull. Soc. d'Hist. Nat, 

 d'Autun iv, 1891. 



Perhaps this is a well-developed form of 0. gracile, from 

 which it seems to differ in being longer and more slender.. 

 It has not been figured. 



41. 0. FILIFORME Moellendorff. PI. 19, fig. 22. 



Shell rimate, very slenderly turrite, thin, finely and very 

 closely striatulate, glossy, pellucid, whitish; spire gradually 

 tapering, the apex a little obtuse. Whorls 7%, a little con- 

 vex, slowly increasing, separated by a rather impressed suture. 

 Aperture moderately oblique, narrowly acuminate-oval; peri- 

 stome unexpanded, acute; columellar margin a little thick- 

 ened, reflexed. Length 5.5, diam. 1.5 mm. (Mlldff.) 



Samui Is., Gulf of Siam. (C. Roebelen). 



Opeas filiforme MLLDFF., Proc. Zool. Soc. Lond. 1894, p. 15, 

 pi. 16, f. 11. 



' ' I do not know of any similar small and slender species of 

 Opeas. The comparatively great number of whorls shows 

 that it is adult." 



42. 0. DIDYMA (Westerlund). PI. 19, fig. 13. 



Shell rimate, subulate, closely, finely striate, the striae 

 curved outwardly, vitreous, rather glossy, the apex obtuse. 

 Whorls iy 2 , the upper convex, the first subcylindric, the 

 rest a little convex, all rather truncate above, separated by 

 a deep, margined, crenulate suture which is horizontal above, 

 then oblique. Aperture subtrigonal-piriform, obtuse at base, 

 the slightly oblique parietal wall forming a deep angle with 

 the columella; columellar margin nearly straight, not trun- 

 cate at base, reflexed, nearly closing the perforation; right 

 margin lightly curved. Length scarcely 8, diam. 2.5 mm. 

 (West.) 



Singapore (Vega Exped.). 



Stenogyra didyma WESTERL., Vega-Expeditionens Veten- 

 skaplige Arbeten, iv, p. 197, pi. 3, f. 9 (1887) ; Nachrbl. 1883, 

 p. 51. 



