WEST AMERICAN PYKAMIDELLID MOLLUSKS. 157 



ODOSTOMIA (CHRYSALLIDA) PROXIMA de Folin. 



Plate 16, fig. 7. 

 Noevila proxima de Folin, Fonds de la Mer, vol. 2, 1872, pp. 166, 167, pi. 6, fig. 3. 



Shell ovate, conic, crystalline. Nuclear whorls one and one-half, 

 obliquely immersed in the first of the succeeding turns. Post- 

 nuclear whorls strongly constricted at the sutures, moderately 

 shouldered at the summit, marked by strong vertical axial ribs, of 

 which 20 occur upon the second and third and 22 upon the penulti- 

 mate turn. These ribs disappear at the periphery. The spaces 

 between the ribs are marked by spiral cords a little less strong than 

 the ribs; four of these occur between the sutures on the second and 

 third, and seven upon the penultimate turn. Their intersections 

 with the ribs form nodules. Sutures channeled. Base somewhat 

 attenuated, marked by eleven spiral cords, the spaces between which 

 are axially lirate. Aperture subpyriform, posterior angle obtuse; 

 outer lip thin, showing the external sculpture within; columella 

 slender, somewhat curved and reflected, provided with a strong fold 

 at its insertion; parietal wall covered with a thin callus. 



De Folin's type was collected at Margarita Island, Bay of Panama. 

 It has four post-nuclear whorls and measures: Length 2.5 mm., 

 diameter 1 mm. 



ODOSTOMIA (CHRYSALLIDA) TYLERI, new species. 

 Plate 16, fig. 5. 



Shell robust, subdiaphanous to milk-white. Nuclear whorls 

 smooth, immersed in the first of the succeeding turns, above which 

 only a part of the decidedly tilted edge of the last whorl projects. Post- 

 nuclear whorls flattened, slightly excurved at the summit, scarcely at 

 all contracted at the periphery and moderately shouldered at the 

 summit, marked by very strong, rounded, axial ribs, of which 14 

 occur upon the first, 16 upon the second, IS upon the third, 20 upon 

 the fourth, 22 upon the fifth, and 24 upon the penultimate turn. In 

 addition to the axial ribs the whorls are marked by spiral cords, less 

 strong than the ribs, the junctions of which with the ribs render them 

 tuberculate. Of these cords, four occur upon all the whorls but the 

 penultimate and last, which have five between the sutures. The 

 spaces inclosed between the ribs and cords are deep square pits. 

 The posterior cord is on the summit of the whorl and is a little 

 stronger than the rest, rendering the whorls, wliicli are excurved, 

 crenulated. Suture well marked but not channeled. Periphery 

 and the somewhat attenuated base of the last whorl well rounded, 

 marked by seven strong, rounded, spiral cords which diminish succes- 

 sively in size and spacing from the peri]:>hery to the umbilical area. 

 The channels which separate the cords are marked b}^ numerous fme 



