ARNOLD — THE PALEONTOLOGY AND STRATIGRAPHY OF SAN PEDRO. 327 



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

 (Arnold). 



Pliocene. — San Pedro (Arnold). 



Subgenus Omphalius Philipjn. 



Shell convex-trochiform, uuibilicated; whorls with revolving series of granules; the last 

 uhurl bluntly angulated at the periphery; umbilicus encircled by a callosity; columellar lip termi- 

 nated by a tooth anteriorly, below which are small tubercles; outer lip usually internally grooved. 



Clilorodoma viridnlus Gmel. is a characteristic sjjecies. 



377. Chlorostoma (Omphalius) viridulum var. ligulatum Menke. 



Trochus ligulahis Menke, Zeit. f. Mai., 1850, p. 173. Fischer, Coq. Viv., p. 382, PI. CXV, hg. 5. 



Omphalius ligulahis Menke, Cpr., Cat. Mazatlan Shells, p 235. 



Omphalius fusccsccns Phil., Cpr., Proc. Zool. Soc, 1S56, p. 224. Cpr., Brit. Assn. Rept., 1S63, 



p. 652. Cooper, 7th Ann. Rept. Cal. St. Min., 1888, p. 255. Keep, West Coast 



Shells, p. 82, fig. 68, 1892. 

 Tiockus luridus Nutt., Cpr., mss., Brit. Assn. Rept., 1856, p. 233. 

 Chlorostoma (^Omphalius) viridulum var. ligulatum Menke, Trvon, Man. Conch., Vol. XI, p. 177, 



PI. XXIX, figs. 58-60, 1889. Dall, Proc. U. S. Nat. Mus., Vol. XV, 1892, p. 200. 



Shell turbinated, thick; whorls five, conve.x to nearly flat; body-whorl subangular at base; 

 ornamentation consists of seven to eight prominent nodose spiral ridges; suture distinct, sometimes 

 quite deeply impressed; base flat, with ornamentation same as whorls, except less prominent; 

 umbilicus deep, effuse, smooth; outer lip eftuse, denticulated on lower portion. 



Dimeiisions. — Alt. 17 mm.; lat. 18 mm.; defl. 80 degrees. 



Some of the specimens show the mottled coloration of the live shell. 

 Distinguishable by denticulation and ornamentation. 



Rare in lower San Pedro series of Deadman Island and San Pedro; common 

 in the upper San Pedro series of Los Cerritos and Crawfish George's; but rare in the 

 upper San Pedro series of Deadman Island and San Pedro. 



Livincj. — Catalina Island to San Diego (Cooper): Mazatlan (Carpenter). 



Pleistocene. — San Pedro (Cooper; Arnold). 



Genus Thalotia Gray. 



.Shell ovate-turriculated, rather thick; not umbilicated; whorls flattened, with revolving ribs, 

 which are sometimes granulated; aperture subrotund; columella tuberculated, truncate in front; outer 

 lip rather thick, crenulated within. 



Thtilotia conicus Gray is a characteristic species. 



378. Thalotia caffea Gabb. 



Turcica I Ptychstylis) caffea Gabb, Proc. Cal. Acad. Sci., Vol. Ill, 1865, p. 187; Pal. Cal., Vol. II, 



pp. 16, 84, PI. Ill, hg. 27, 1869. 

 Thalotia caffea Gabb, Cooper, Geog. Cat. West Coast Shells, p. 26, 1S67. CooPER, 7th Ann. 



Rept. Cal. St. Min., 1888, p. 267. 



