1917.] 



NATURAL SCIENCES OF PHILADELPHIA. 



323 



and the third smaller, below the periphery. The aperture is ovate; 

 columellar fold deeply immersed. 



Length 1.9, diam. 0.9 mm. 



Four specimens, of which the most perfect has been selected for 

 type and figure. The largest is more than twice the size of this one, 

 but the base and aperture are broken. It belongs to the subgenus 

 Cydodostomia , apparently. 



Odostomia suta. 



Fig. 23. — Odostomia lelsonce. 



Odostomia letsonae n. sp. Fig. 23. 



Paumalu, Oahu. Type No. 117600, A. N. S. P., collected by 

 Mrs. A. F. Letson. 



The shell is oblong-conic, white, Nuclear whorls are worn. The 

 rest of the- whorls of the spire have two broad, rounded, contiguous 

 spiral ridges in the upper part. In the last whorl the ridges are more 

 separated, the lower one being narrower and median on the whorl; 

 there is also a third and smaller ridge around the axial region. Over 

 the whole surface there is a dense microscopic spiral striation. The 

 aperture is oblique, the outer lip irregular. The columella is very 

 thick, but shows no fold. 



Length 2.6, diam. 1.1, length of aperture 0.85 mm.; 8 whorls. 



The subgeneric position of this strongly sculptured little Odostomia 

 is not clear to me. In Dr. Bartsch's key it comes nearest to Cydo- 

 dostomia. It was picked from beach debris by Mrs. Letson, whose 

 work on the minute shells of this locality has brought many inter- 

 esting species to light. 

 Odostomia (Odostomia) kahoolawensis n. sp. Fig. 24. 



Northern shore of Kahoolawe. T\pe No. 116166, A. N. S. P., 

 coll. by Pilsbry, 1913. 



The shell is imperforate, conic, grayish white, with some opaque 



