296 CALIFOKNIA ACADEMY OF SCIENCES. 



321. Bittium ^Styliferina) tenuisculpta Cmyenter. 



Plate VI, Fig. 14. 



Shell small, conical, turreted, thin, diaphanous; apex sharp; whorls ten, rounded, nearly 

 smooth, but showing faint spiral sculpture; suture deep, distinct; body-whorl evenly rounded below; 

 aperture subrotund; outer lip thin; inner lip simple. 



Ditnensiotts. — Long. 5 mm.; lat. 2 mm.; body-whorl 2.5 mm.; aperture 7.5 mm.; defl. 

 20 degrees. 



Specimens identified by Dr. Dall. 



Rare in lower San Pedro series of San Pedro; one specimen found, wiiich is 

 figured, and is now in the collection of Delos Arnold. 



Living. — West Coast (?). 



Pleistocene. — San Pedro (Arnold). 



Genus Diastema Deshayes. 



Shell turreted; whorls with numerous transverse ribs, and with a few intermediate varices; 

 inner margin of the aperture partially detached from the previous whorl; the aperture itself is 

 strongly contracted posteriorly. 



322. Diastema, sp. indet. 



Shell small, regularly conical, turreted; whorls seven, convex, ornamented with eleven 

 slightly oblique transverse ridges, which are most prominent on the angle of the whorl and become 

 obsolete at the sutures; suture deeply impressed; aperture broadly elliptical; outer lip thin; inner lip 

 smooth; canal short. 



Ditnensions. — Long. 10.5 mm.; lat. 4.5 mm.; body-whorl 5.8 mm.; aperture, 4 mm.; defl. 

 28 degrees. 



The above description was taken from a shell which Dr. Dall pronounced a 

 young of the genus Diastoma. 



Lower Pleistocene of San Pedro, only one sjiecimen. A specimen of the 

 same species (?) was found in the Pleistocene at the bath-house, Santa Barbara. 



Pleistocene. — San Pedro; Santa Barbara (Arnold). 



Genus Cerithidea Sivainson. 



Shell turriculated, longitudinally ribbed; whorls numerous; summit of spire more or less 

 decollated; aperture rounded, slightly slit anteriorly; outer lip expanded, thickened, broadly rounded 

 below, and usually produced into a beak crossing the sinus to the left. 



Cerithidea decollntvm Linn, i.s a characteri.stic species. 



323. Cerithidea calif ornica Haldemann. 



Cerithiutn calif or ytiattn Hald., Fr. W. Univ. Moll, cover of No. i, 1840. 



Cerithium {Potamis) sacra/um Glv., Proc. Bost. Soc. Nat. Hist., Vol. Ill, 1849, p. 118; Wilkes' 



Expl. Exped., Vol. Xll, p. 114, PI. X, fig. 116, 1852. Tkvon, Man. Conch., 



Vol. IX, p. 162, PI. XXXIII, fig.s. 69-72, 1887. 



