138 PROCEEDLXnS OF THE NATIONAL MUSEUM. vol. xxxi. 



As Doctor Pilsbry has pointed out/' there is a weak, short fold, 

 more like a tooth upon the axis, in the penultimate whorl, near the 

 basal wall. There is also a weak submedian twist, which extends 

 through th(^ spire. The ribbing- of the exterior varies from ver}'- 

 decided, as shown in the figure of the type,^ to sul)obsolete on the 

 middle of the cylindrical portion, as shown by Doctor Pilsbry's figure/ 



HOLOSPIRA (BOSTRICHOCENTRUM) HIDALGOENSIS, new species. 



Plate IV, fig. 12. 



Shell slender, elongate, c^iindric-conic, white. Terminal cone grad- 

 ually tapering. Nuclear whorls 3, moderately rounded, increasing 

 regularly in size, very minutely granulose. The tirst nuclear whorl 

 is broad and lends the apex a somewhat truncated appearance. Suc- 

 ceeding whorls flattened, the earl}^ ones of the terminal cone slightly 

 overhanging, alf marked by strong, curved, somewhat distantly spaced 

 sublamellar ribs, of which about 28 occur upon the first sculptured 

 whorl (i. e., the fourth whorl), -±0 upon the tenth, and 26 upon the 

 penultimate whorl. The ribs are placed closest posteriorly and 

 become gradually more distantly spaced toward the penultimate 

 whorl. The wide spaces between the ribs are crossed b}^ several 

 irregular secondary riblets, which lend them a longitudinally crinkled 

 appearance. Periphery of the last whorl somewhat angulated. Base 

 well rounded; the strong continuation of the ribs extend into the 

 umbilical rimation. The last portion of the last whorl free for about 

 3 mm. Parietal wall somewhat pinched a little to the left of its junc- 

 tion with the outer wall, which lends the posterior lateral angle a 

 slightly carinated appearance. The free parietal w^all is marked by 

 the continuation of the ribs, which are less strongl}^ developed and 

 more closely crowded immediately behind the aperture. Aperture 

 subquadrate, parietal border somewhat sinuous, owing to the pinched 

 portion alluded to above; peristome decidedly expanded, but not re vo- 

 lute. Internal pillar slender, bearing an obsolete submedian spiral 

 twist that is strengthened to form a low lamella, which extends through 

 the antepenultimate whorl. There are two specimens in the collection 

 of the U. S. National Museum, Cat. No. 1S70S2, donated l)y A. L. 

 Herrera. They were collected at Zimapan, Hidalgo, Mexico. 



«Proc. Acad. Nat. Sci. Philadelphia, 1905, p. 217. 

 &Proc. U. S. Nat. Mus., XIX, 1896, j)l. xxxi, fig. 2. 

 cProc. Acad. Nat. Sci. Philadelphia, 1905, pi. xxvi, fi^ 



