174 BULLETIN 68, UNITED STATES NATIONAL MUSEUM. 



between the sutures, while a third equally acute keel marks the 

 periphery of the last whorl. Two other keels ornament the base, 

 the anterior one of which is not quite as strong as its neighbor. The 

 axial sculpture consists of narrow, more or less lamellar, almost 

 vertical ribs, which render the intersection with the spiral keels 

 somewhat thickened, but not nodulose. These axial ribs extend over 

 the periphery and base of the last whorl to the umbilical region, grad- 

 ually growing weaker as they approach this point. There are about 

 18 on the second and 20 upon the penultimate whorl. The spaces 

 between the ribs and keels appear as concave quadrangular depres- 

 sions. Umbilicus narrowly perforated. Suture deeply channeled 

 by the shouldered whorl. Aperture suboval, posterior angle decidedly 

 obtuse; outer lip thick, marked by 5 projections, corresponding to 

 the 5 keels; columella almost straight, strongly re volute with a 

 conspicuous oblique fold near its insertion; parietal wall covered by 

 a faint callus showing both basal keels, the anterior faint and just pos- 

 terior to the insertion of the columella and the next on the middle of 

 the wall. 



The tji:)e has 5 post-nuclear whorls and measures: Length 2.7 mm., 

 diameter 1.3 mm. It and three additional specimens (Cat. no. 

 106502, U.S.N.M.) were collected by Mr. Henry Hemphill at Scam- 

 mon Lagoon, Lower California. Three additional lots are in the LT. S. 

 National Museum collection: Cat. no. 129336, 30 specimens collected 

 by Mrs. T. S. Oldroyd in the drift at San Pedro; Cat. no. 162843, 3 

 specimens also from San Pedro by the same donor; Cat. no. 62844, 

 1 specimen collected by Mr. Henry Hemphill at Ocean Beach, San 

 Diego, California. 



ODOSTOMIA (IVIDELLA) NAVISA DELMONTENSIS Dall and Bartsch. 



Plate 18, figs. 10, 10«. 



Odostomia (Ividia) navisa delmontensis Dall and Bartsch, Proc. U. S. Nat. 

 MuB., vol. 33, 1907, p. 518, pi. 4G, figs. 3, 3fl. 



Shell similar to 0. (/.) navisa but more elongate, and in every way 

 more delicate, with the lamellose sculpture reduced almost to raised 

 cords and with stronger shouldered summits and more open umbilicus. 



The type (Cat. no. 196297, U.S.N.M.) was collected by Mr. S. S. 

 Berry in 12 fathoms, off Del Monte, Monterey Ba^^, California. It 

 has five post-nuclear whorls and measures: Length 3.2 mm., diam- 

 eter 1.3 mm. 



ODOSTOMIA (IVIDELLA) QUINQUECINCTA Carpenter. 



Plate 18, fig. 9. 

 Parthenia quinquecincta Carpenter, Cat. Mazatlan Shells, 1856, p. 414. 



Shell elongate-ovate. Nuclear whorls tumid, obliquely immersed. 

 Post-nuclear whorls flattened, strongh^ tabulatedly shouldered at the 



