NO. 1903. WEST AMERICAN PYRAMIDELLID MOLLUSKS—BARTSCH. 277 



immediately above tlie periphery, while the first is as far below the 

 summit as the third is posterior to the fourth. The second line 

 divides the space between the first and third into equal halves, which 

 are about one and a half times as wide as the spaces included between 

 the tliird and fourth incised spiral. In addition to the spiral sculpture 

 the whorls are crossed by numerous, fine, decidedly retractive, incre- 

 mental lines. Periphery of the last whorl somewhat inflated, well 

 rounded. Base moderately long and moderately rounded, crossed 

 by 8 strongly incised, equal, spiral lines, which are a little stronger 

 than those occurring on the spire. These lines become exceedingly 

 closely spaced between the periphery and the umbilical area. The 

 axial sculpture on the base is of the same character and strength as 

 that appearing on the spire. All of the incised, spiral lines on base 

 and spire are crossed by very slender, axial threads, which lend these 

 channels a somewhat pitted appearance. Sutures well impressed. 

 Aperture moderately large, oval, effuse anteriorly; posterior angle 

 acute; outer lip thin, showing the external sculpture within; inner 

 lip oblique, moderately long, somewhat reflected, and reenforced 

 for the greater part of its length by the attenuated base, pro\T[ded 

 with an obUque fold at its insertion; parietal wall glazed with a 

 thin callus. 



The type (Cat. No. 194518, U.S.N.M.) comes from Catalina Island, 

 California, It has lost the nucleus and probably a portion of the first 

 post-nuclear turn; the five remaining measure: Length, 3.9 mm.; 

 diameter, 1.9 mm. 



This species follows Odostomia ( Menestho) callipyrga in the key. 



ODOSTOMIA (EVALEA) YOUNGI Dall and Bartsch. 



Plate 37, %. C. 



Odostomia (Evalea) youngi Dall and Bartsch, Dep. Mines, Geol. Surv., Canada, 

 1910, pp. 16-17, pi. 2, fig. 1. 



Shell, elongate-conic, umbilicated, milk-white. Nuclear whorls 

 small, obliquely immersed in the first of the post-nuclear turns, above 

 which only the tilted edge of the last volution projects. Post- 

 nuclear whorls moderately rounded, with a narrow tabulatedly 

 shouldered summit, marked by equally spaced, rather strong, spiral 

 striations, of which about 32 occur between the summit and the 

 periphery on the penultimate turn. Periphery and base of the last 

 whorl inflated, well rounded, marked with spiral sculpture equal in 

 strength and disposition to that on the spire. Sutures strongly 

 impressed. In addition to the spiral sculpture, the whorls are marked 

 with curved retractive lines of growth. Aperture pear-shaped; pos- 

 terior angle acute; outer lip thin; inner hp slender, curved, and 

 somewhat revolute, jirovided with a strong oblique fold a little 

 anterior to its insertion; parietal wall glazed with a thick callus. 



