ARNOLD — THE PALEONTOLOOY AND STKATIGRAPnY OF SAN PEDRO. 331 



Found ill upper San Pedro scries of Siui Pedro, Los Cerritos, and Crawfish 

 Goorije's. Found in llic I'liooene at Packard's Hill, Santa Barbara; and in tlie 

 Pleistocene at Spanish liight, San Diego. 



Living. — San Pedro to San Diego (Cooper). 



Pleistocene. — San Pedro to San Diego (Cooper): San Pedro; San Diego, 

 (Arnold). 



Pliocene. — Santa Barbaia (Arnold). 



384. Calliostoma tricolor Gabb. 



Ca/liostoma tricolor Gabb, Proc. Cal. Acad. Sci., Vol. Ill, 1.S65, p. 186; Pal. Cal., Vol. II, p. 17, 

 PI. Ill, fig. 28, 1869. Cooper, 7th Ann. Rept. Cal. St. Min., 1888, p. 231. Tryon, 

 Man. Conch., Vol. XI, p. 370, PI. LXVII, fig. 52, 1889. Keep, West Coast Shells, 

 p. 82, 1892. Williamson, Proc. U. S. Nat. Mus., Vol. XV, 1892, PI. XIX, fig. 8. 



Shell conical; spire elevated, subacute; whorls five to si.x, flat to concave, with prominent, 

 rounded keel on anterior margin; surface ornamented with fine sjjiral lines; suture impressed, dis- 

 tinct; base nearly flat, ornamented with tine spiral ridges and furrows; aperture subcircular; outer 

 li[) thin; columella slightly incrusted. 



Dimensions. — Alt. 11 nun.; lat. 11 mm.; defl. 66 degrees. 



Distinguishable by the prominent, smooth keel on the anterior part of 

 whorls; and by the concavity and inconspicuous ornamentation of the upper part 

 of the whorls. 



Rare in the Pliocene at Deadmaii Island; in lower San Pedro series at San 

 Pedro; and in upper San Pedro series of Crawfish George's, San Pedro, and Los 

 Cerritos. Found in the Pleistocene at Spanish Bight, San Diego. 



Living. — New Year Point to San Diego (Cooper): San Pedro (Arnold). 



Pleistocene. — San Pedro to San Diego (Cooper): San Pedro; San Diego 

 (Arnold). 



Pliocene. — San Pedro (Arnold). 



Gemis Norrisia Bayle. 



Shell thick, conoidal, orbicular, covered by an epidermis, smooth; widely umbilicated, umbili- 

 cus surrounded by the callous extension of the columella; outer lip not thickened or sculptured within. 



Norrisia norrisii Sby. is a characteristic species. 



385. Norrisia norrisii Soiverby. 



Trochischus norrisii Sby., Tank. Catalogue, 1825. Cpr., Brit. Assn. Rept., 1863, p. 652. 

 = T. convexus Cpr. {fide Gabb, Pal. Cal., Vol. II, p. 85, 1869). Tryon, Syst. and 

 Struct. Conch., Vol. II, p. 315, PI. LXXXI, fig. 64, 1883. Cooper, 7th Ann. Rept. 

 Cal. St. Min., 1S8S, p. 268. Keep, West Coast Shells, p. 86, fig. 72, 1892. 



Norrisia norrisii Sky., Dall, Proc. U. S. Nat. Mus., Vol. XV, 1892, p. 200. 



Shell of medium size, conoidal, orbicular, thick; s|)ire only slightly elevated above body- 

 whorl; whorls three or four, only very slightly convex, smooth except for lines of growth; suture 



