no. 1826. MOLLUSKS OF THE GENUS BITTIUM— BARTSOH. 387 



The type (Cat. No. 32271, U.S.N.M.) comes from Panama. It has 

 twelve post-nuclear whorls and measures: Length 14 mm., diameter 

 4.1 mm. 



BITTIUM (BITTIUM) JOHNSTONS, new species. 

 Plate 53, fig. 6. 



Shell very elongate-conic, chestnut brown with strong white varices 

 at irregular intervals. (Nuclear whorls decollated.) Post-nuclear 

 whorls well rounded, the early turns ornamented with four spiral 

 keels, all of which, except the anterior one, which is at the summit, 

 are of equal size and about as wide as the spaces that separate them; 

 the one at the summit being much more slender. On the last three 

 whorls the keel at the summit divides into two slender threads, 

 which occupy the same amount of space as the single keel does on the 

 earlier turns. In addition to the spiral keels, the whorls are marked 

 by strong, well-rounded, axial ribs which are about two-thirds as 

 wide as the spaces that separate them. These ribs render the spiral 

 keels tuberculate at their intersection. There are 12 ribs upon the 

 third, 14 upon the fourth, 16 upon the fifth and sixth, and 18 upon 

 the seventh turn. On the last two whorls, four axial ribs occur 

 between each pair of varices. Varices very large and conspicuous. 

 Sutures strongly constricted. Periphery of the last whorl well 

 rounded, marked by a slender spiral cord which is not tuberculate. 

 Base rather prolonged, well rounded, marked by four equal and 

 equally spaced spiral cords, of which the last is immediately behind 

 the columella. Entire surface of base marked by numerous, rather 

 strong lines of growth. Aperture ovate, decidedly channeled ante- 

 riorly; outer lip thin at the edge, rendered sinuous by the external 

 sculpture which is visible within; columella very short, curved, and 

 covered on its entire surface by a strong callus, which also extends 

 over the parietal wall. 



The type (Cat. No. 196208, U.S.N.M.) was collected by Mrs. E. E. 

 Johnston in Lower California. It has ten whorls and measures: 

 Length 7.9 mm., diameter 2.6 mm. 



Named for Mrs. E. E. Johnston. 



BITTIUM (STYLIDIUM) ESCHRICHTII Middendorfl. 



Plate 58, fig. 4. 



Cerithium filosum Gould, Proc. Boston Soc. Nat. Hist., vol. 3, 1849, p. 120, not 



of Philippi, Zeitschr. fur Mai., 1848, p. 143. 

 Turritella eschrichtii Middendorff, Beitr. Mai. Ross., vol. 2, p. 68, pi. 11, fig. 1, 



1849. 

 Bittium filosum Carpenter, Rep. Brit. Ass. Adv. Sci. for 1863, 1864, p. 655. — 



Arnold, Pal. and Strat. San Pedro, 1903, p. 292. 

 Bittium (Stylidium) eschrichtii Dall, Proc. U. S. Nat. Mus., vol. 33, No. 1564, p. 



178, Oct., 1907. 

 Bittium (Stylidium) eschrichtii Dall, Prof. Paper 59, U. S. Geol. Surv., p. 76, pi. 14, 



fig. 2, 1909. 



