ARNOLD — THE PALEONTOLOGY AND STUATICRArilY OF SAN I'KDIiO. 331 



Fouiul in upper San Pedro series of San Pedro, Los Cerritos, and Crawfish 

 George's. Found in the Plioeene at Packard's Hill, Santa Barl)ani; and in the 

 Pleistocene at Spanish Bight, San Diego. 



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



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

 (Arnold). 



Pliocene. — Santa Barbara (Arnohl). 



384. Calliostoma tricolor Gabb. 



Calliostoma tricolor Gabb, Proc. Cal. Acad. Sci., Vol. Ill, 1865, p. 186; Pal. Cal., Vol. II, p. 17, 

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

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

 p. 82, 1892. WiLLiAMSO.N, 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 spiral lines; suture impressed, dis- 

 tinct; base nearly flat, ornamented witii fine sjjiral ridges and furrows; aperture subcircular; outer 

 lip thin; columella slightly iacru.sted. 



Dimensiotis. — Alt. 1 1 mm. ; lat. 1 1 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 Deadman 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). 



Genus Norrisia Bayle. 



Shell thick, conoidal, orbicular, covered by an e|)idermis, 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 Sowerby. 



Trochischus norrisii Sbv., Tank. Catalogue, 1825. Cpr., Brit. A.ssn. 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., 1888, p. 268. Keep, West Coast Shells, p. 86, fig. 72, 1892. 



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



Shell of medium size, conoidal, orbicular, thick; spire only slightly elevated above body- 

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



