WEST AMEETCAN PYRAMIDELLID MOLLUSKS. 187 



fering from P. cxanitu in the niiinlior and strength of spiral ridges. 

 Length 0.65 mm., diameter 0.55 mm. One specimen was taken 

 from Chama at Mazatlan, Mexico." 



From an examination of the type we are able to add that it is a 

 much worn, young, and distorted Menestho. 



ODOSTOMIA (MENESTHO) RECTA de Folin. 

 Odetta recta de Folin, Les Fonds dc la Mcr, vol. 2. 1872, pp. 167, 108. 



Shell conic, ventricose, subcrystalline, robust, with straight spire. 

 Nuclear whorls three, forming an acute apex, having their axis at 

 right angles to that of the succeeding turn. Post-nuclear whorls 

 four, marked by three broad, strong, somewhat rounded, spiral keels 

 between the sutures, the spaces between which are less wide than 

 the keels. Sutures ill defined. Last whorl almost equal to half the 

 length of the shell. Base marked by less developed spiral cords. 

 Aperture oval; columella provided with a strong fold. 



De Folin's type, which was unfortunately crushed by him while 

 being drawn, comes from the Margarita Island, Bay of Panama.. It 

 had four post-nuclear whorls and measured : Length 2.0 mm. , diameter 

 LI mm. 



ODOSTOMIA (MENESTHO) AMILDA, new species. 

 Plate 21, lig. 4. 



Shell ovate, transparent. Nuclear whorls deeply obliquely 

 immersed in the first of the succeeding turns, above wliich only 

 the tilted edge of the last whorl projects. Post-nuclear whorls well 

 rounded, slightly contracted at the sutures, and somewhat shoul- 

 dered at the summits, the first marked by four slender equal and 

 subequally spaced incised spiral lines; the rest are marked by a 

 stronglv incised groove a little below the summit which causes this 

 to appear bounded by a well-rounded cord; the remainder of the 

 whorls between the sutures show a few distantly spaced and feebly 

 incised sjnral lines and numerous very fine, decidedly retractile 

 lines of growth. Periphery of the last whorl well rounded. Base 

 somewhat inflated, well rounded, slightly attenuated anteriorly, 

 marked by numerous exceedingly fine, microscopic s})iral striations 

 and three well incised equal and equally spaced lines on the anterior 

 half. Aperture oval, somewhat effuse anteriorly; posterior angle 

 obtuse; outer lip thin, showing the external sculpture within; col- 

 umella slender, decidedly curved, somewhat reflected, reenforced by 

 the base; provided with a strong fold at its insertion. 



The type (Cat. no. 60905, U.S.N.M.) comes from San Diego, 

 CaUfornia. It has four post-nuclear whorls and measures: Length 

 2.6 mm., diameter L3 mm. Two additional specimens (Cat. no. 

 206907, U.S.N.M.) come from Round Island, Lower California. 



