no. 1826. MOLLUSKS OF THE GENUS BITTIUM— BARTSCH. 411 



two of the first post-nuclear turns) and measures: Length 18.8 

 mm., diameter 0.5 mm. An additional specimen (Cat. No. 195128, 

 U.S.N.M.) comes from the Pleistocene of San Pedro, California. 



BITTIUM CASMALIENSE, new species. 

 Plate 55, fig. 3. 



Shell very large and robust, white. Nucleus and early post-nuclear 

 whorls decollated. Post-nuclear whorls marked by four equal and 

 almost Equally spaced, strong, spiral cords which divide the space 

 between the sutures into four almost equal areas. The first of these 

 cords is at the summit. In addition to the spiral cords, the whorls 

 are marked by strong, well rounded, almost vertical, axial ribs, of 

 which 14 occur upon the second, 16 upon the third and fourth, 18 

 upon the fifth, 20 upon the sixth, while upon the penultimate and last 

 of the remaining turns they become obsolete and irregular. The 

 axial ribs are fully twice as strong as the spiral cords and the inter- 

 sections of the two form well rounded, elongate tubercles, the long 

 axes of which coincide with the spiral sculpture. The spaces inclosed 

 between the spiral cords and axial ribs are very deeply impressed, 

 oval pits on the early whorls, while on the later ones they are shallow, 

 rectangular pits. Sutures moderately constricted, showing a portion 

 of the peripheral cord. Periphery of the last whorl well rounded, 

 marked by a well rounded, slender, spiral cord. Base well rounded, 

 marked by a single cord a little less strong than the peripheral, and 

 a little nearer the peripheral cord than that is to the cord posterior 

 to it. Aperture fractured, channeled anteriorly; posterior angle 

 obtuse; columella stout and somewhat twisted. 



The type (Cat. No. 165279, U.S.N.M.) has the last seven whorls 

 and measures: Length 18 mm., diameter 6 mm. It comes from the 

 Fernando Formation, Lower Pliocene, at the railroad cut, 1 mile 

 north of Schumann, Santa Barbara County, California. 



BITTIUM ARNOLDI, new species. 



Plate 56, fig. 1. 



Shell very large, broadly elongate-conic, white. (Nucleus and 

 early post-nuclear whorls decollated.) The remaining whorls with 

 appressed summit, marked by four strong, spiral cords which divide 

 the space between the sutures into four equal parts. The first of 

 these cords is at the summit. The spaces between the strong spiral 

 cords are divided by intercalated spirals which are well developed, 

 but not quite as strong as the primary cords. On the last turn two 

 of these intercalated spirals occur between all but the third and 

 fourth below the summit, where three are present. In addition to 

 the spiral sculpture, the whorls are marked by moderately strong, 

 curved, well rounded, axial ribs, of which 14 occur upon the third 



