ARNOLD— THE PALEONTOLOGY AND STUATIGHAPUY OF SAN PEDRO. 275 



exposed portions of the whorl; aperture large, ovate, somewhat produced at the base; posterior 

 angle acute: outer lip thin, joining the oblique, strongly revolute columella in a wide curve; the 

 strongly reflexeii columella and the decided rounding of the last whorl give the shell a subumbili- 

 cated appearance; the peritreme is rendered almost complete by the strong callus which extends 

 from the posterior angle of the aperture to the insertion of the columella; by transmitted light the 

 interior of the outer lip appears beautifully marked by narrow, wavy, sometimes branching, spiral 

 threads of red, laid on a ground of pale yellow, the middle one of which is the broadest, and marks 

 the periphery. 



Dimensions. — Long. 7.2 mm.; diam. 1.9 mm. 



The type is from Scamtnou's Lagoon, Lower California, and has twelve post- 

 nuclear whorls. 



This species also occurs recent along the California coast, and has been found 

 as a post-Pliocene fossil at San Diego. 



292. Turbonilla (Pyrgiscus) latifundia D. <C- B., sp. nov. 



Pl.\tk III, Fit:s. 5 and 5a. 



Shell very broadly conic, milk-white; nuclear whorls two and one-half, with moderately 

 elevated spire, extending a little beyond the outline of the first post-nuclear whorl on one side, about 

 one-third immersed, their axis being at a right angle to the a.xis of the later whorls; post -nuclear 

 whorls well rounded, each much broader at its base than the summit, ornamented by about fourteen 

 strong, rounded, oblique, axial ribs and seven or eight deeply impressed, very prominent spiral 

 lirations, extending across the intercostal spaces, which are about twice as wide as the ribs, and upon 

 the sides of these, but they do not cross their summits; both ribs and intercostal spaces pass very 

 feebly over the decidedly angulated periphery (this angulation is much more pronounced in young 

 specimens than in the adult); the short base is marked by about seven continuous, somewhat wavy, 

 subequally spaced, spiral lines, much weaker than the spiral sculpture on the exposed portion of the 

 whorls; aperture subquadrate, posterior angle acute; outer lip thin, showing the external sculpture 

 within by transmitted light; columella straight and revolute. 



Ditnensiotis. — Long. 5.8 mm.; long, spin 5.2 mm.; diam. 2 mm. 



The type is a post-Pliocene fossil from San Pedro, and has nine post- 

 nuclear whorls. 



This species occurs also in the post-Pliocene deposits of Deadman Island. 

 So far no recent representatives have been found. 



293. Turbonilla (Pyrgiscus) tenuicula Gould. 



Plate II, Figs. 7 a.sd 7a. 



Chemnitzia tenuicula Gld., Bost. Jour. Nat. Hist., Vol. VI, 1853, pp. 383, 384, PI. XIV, fig. 15. 



Shell small, elongated, lanceolate, turreted, rather solid, shining, wax yellow, a little dusky 

 below the suture; whorls ten, flat, slightly shouldered above, marked by about twenty direct, longi- 

 tudinal folds, the summits of which are cut by numerous fine revolving striae, deeper in the interstices, 

 which also extend over the base of the shell, though the folds terminate at the periphery, or are 

 extended in delicate furrows; aperture narrow, ovate; lip sharp; revolving stria; apparent within. 

 Dimensions. — Length 7.5 mm.; diam. 1.3mm. 



Found at Santa Barbara. 



