WEST AMEEICAN PYRAMIDELLID MOLLUSKS. 130 



up on the sides of the ribs but do not cross their summits. The 

 spaces between the ribs and cords are well impressed, round pits. 

 Sutures channeled. Periphery of the last whorl marked by a groove. 

 Base well rounded, marked by five subequal and equally spaced 

 spiral cords, the spaces between which are crossed by slender axial 

 threads. Aperture pyriform, posterior angle obtuse; outer lip thm, 

 showing the external sculpture within; columella slender, provided 

 with an oblique fold at the insertion; parietal wall covered with a 

 thin callus. 



Tablet 1979, Liverpool collection, British Museum, contains the 

 type which w^as taken off Spondylus at Mazatlan, Mexico. It has 

 four post-nuclear whorls and measures: Length 1.4 mm., diameter 

 0.7 mm. 



ODOSTOMIA (CHRYSALLIDA) INCONSPICUA C. B. Adams. 



Plate 14, fig. 3. 



Cingula inconspicua C. B. Adams, Ann. Lye. Nat. Hist, of N. Y., vol. 5, 1852, 

 p. 405. . - 



Shell ovoid, milk-white. Nuclear whorls deeply, obliquely im- 

 mersed in the first of the succeeding turns, above which only the tilted 

 edge of the last volution projects, which is smooth. Post-nuclear 

 whorls very slightly rounded, ornamented by strong axial ribs, of 

 which 18 occur upon the second and third and 20 upon the penulti- 

 mate turn. In addition to the axial ribs the whorls are marked by 

 four equal and equally spaced slender spiral cords, which are a little 

 less strong than the ribs, and render the junction with these nodu- 

 lous. Sutures channeled; periphery and base of the last whorl well 

 rounded, the latter marked by six equal spiral cords, which are about 

 as wide as the spaces that separate them. The impressed grooves 

 are crossed by numerous slender axial tlireads. Aperture ovate; 

 posterior angle obtuse; outer lip thin, pinched in in the middle; 

 columella slender, moderately curved, slightly reflected, partly reen- 

 forced by the base. Parietal wall covered with a strong callus, 

 which renders the peritreme complete. 



The type is at Amherst College, and was collected by Prof. C. B. 

 Adams at Panama Bay. It has five post-nuclear whorls and meas- 

 ures: Length 1.5 mm., diameter 0.6 mm. 



ODOSTOMIA (CHRYSALLIDA) TELESCOPIUM Carpenter. 



Plate 13, fig. 9. 



Chrysallida ielescopium Carpenter, Cat. Mazatlan Shells, 1856, pp. 421, 422. 



Shell very elongate-conic, white. Nuclear whorls two, forming a 

 moderately elevated helicoid spire which is about one-half obliquely 

 immersed in the first of the succeedmg turns. Post-nuclear whorls 

 almost flattened, strongly contracted at the suture and strongly 



