ARNOI,!) — THE PALEONTOLOGY AND STRATIGliAPHY OF SAN PEDRO. 2G7 



280. Opalia crenatoides Carpentur, var. insculpta Carpenter. 



Opalia (f crenatoides) var. insculpta Cpr., Hi it. As.sn. Ript., 1S63, p. 660; Ann. & Mas,'. Nat. 

 Hist., 3rd Series, Vol. XVII, 1.S66, p. 277. Cooper, 7th Ann. Rept. Cal. St. Min., 

 1888, p. 255. 



Shell of medium size, elongated, thick, milk-white; spire elevated, with blunt apex; whorls 

 si.x, convex; first and second post-nuclear whorls more convex than the remaining; whorls, angulated, 

 nearly smooth; last four post-nuclear sharply and strongly angulated above, llattened along middle, 

 and quite abruptly contracted at base; whorls ornamented with twelve to fourteen radiating trans- 

 verse ribs, which are obsolete on the sides of the whorl, faintly developed at the base, and strongly 

 developed on the top of the whorl, where they are appressed against the antecedent whorl, and 

 appear like nodes on the angle of the whorl; a faint sutural riblet is sometimes noticeable on the base 

 of the whorl; above this sutural riblet are faint holes, corresponding to the intercostal spaces; fine 

 incremental striations are visible over the whole surface of the shell; the base of the body-whorl, just 

 l)elow the angle, is ornamented with a prominent, wide, elevated rib; aperture elliptical; outer lip 

 thickened, rounded, slightly expanded at columella; this lip is finely, concentrically striated; inner 

 lip rounded, smooth. 



Dimensions. — Long. 16.4 mm.: lat. S.3 mm.; body-whorl 9.9 mm. 



Thi.s species is distinguishable by its broad form and sliarply angidar whorls, 

 wliicdi arc prominently scidptnred above, with obsolete scuilptnre on the sides of the 

 wlioii. Cari)enter's type specimen was a post-Pliocene fossil from Santa Barbara. 



Rare in the upper San Pedro series at Deadman Island. 



Living. — Santa Cruz to Santa Barbara (Cooper). 

 Pleistocene.— SAutii Barbara (Cooi)er) : San Pedro (Arnold). 



[S. 1).] Opalia varicostata Stearns. 



Opalia varicostata Stearns, Proc. Phil. Acad. Nat. Sci., 1875, p. 463, PI. XXVII, figs. 2-5. 

 Cooper, 7th Ann. Rept. Cal. St. Min., 1888, p. 255. Dall, Trans. Wagner Inst. 

 Sci., Vol. Ill, Part 2, 1892, p. 245. 



Shell elongated-conical, turreted, tapering, solid, imperforate; aperture ovate; peristome 

 continuous, thickened; dingy to clear white; suture well defined; whorls united, exceedingly variable 

 in convexity and altitude; specimens all decollate or truncated, equally solid, though varying in 

 length from 20 to 60 millimeters, showing four and one-half whorls within the first measurement to 

 five in the latter; longitudinal ribs nine to twelve, varying in number, prominence and regularity, as 

 well as in obliquity and thickness; suture more or less waved, dependent upon the prominence of the 

 ribs, which terminate anteriorly at and join a transverse (spiral) rib at about the middle of the 

 Ijasal whorl. 



Dimensions of a Rather Small Specimen. — Long. 34 mm.; lat. 14.5 mm.; body-whorl 

 17 mm.; aperture 9 mm. 



This magnificent but variable species has so far been reported only from the 

 Pliocene of San Diego, where it is quite common. 



Pliocene. — San Diego (Hemphill; Stearns; Arnold). 



