322 CALIFORNIA ACADEMY OF SCIENCES. 



Shell of moderate size, conical; spire elevated, subacute; whorls five or six, flat, with numer- 

 ous oblique, rounded, irregular, transverse ridges, with smaller ridges intercalated on lower part of 

 whorls; suture impressed, wavy, distinct; aperture subovate; umbilicus obsolete; base flat, ornamented 

 with several prominent, rounded, rugose spiral ridges with squamose lirulae between. 



Dimensions. — Alt. 23 mm.; lat. 25 mm.; defl. 65 mm. 



Tliis species resembles Pomnulax undosus quite closely, but may be distinguished 

 from that sjiecies by lack of prominent keel on anterior margni of whorl, intercalated 

 transverse ridges, and prominent spiral ridges on base. 



Rare in upper San Pedro series of San Pedro. 



Living. — Straits of Fuca to Catalina Island (Cooper). 



Pleistocene. — Santa Barbara; San Pedro (Cooper): San Pedro (Williamson; 

 Arnold). 



Genus Pomaulax Gnry. 



Shell trochiform, elevated, conic, angulated and nodose at the periphery; obliquely ribbed; 

 not umbilicated; inner lip arcuated with a wide callus, which is channeled, anteriorly truncated. 



Type, Pomaulax undosus Wood. 



367. Pomaulax undosus Wood. 



Trochus undosus Wood, Inde.x, Test. Suppl., PI. LI, fig. i, 182S; Suppl., p. 16, PL V, fig, i, 1859. 

 Pomaulax undosus Wood, Cpr., Brit. Assn. Rept. , 1863, p. 651. Gabb, Pal. Cal., Vol. II, p. 83, 



1869. Tryon, Man. Conch., Vol. X, p. 243, PI. LVIII, figs. 69, 70, 1SS8; Syst. and 



Struct. Conch., Vol. II, p. 308, PI. LXXX, fig. 33, 1883. Cooper, 7th Ann. Rept. Cal. 



St. Min., 1888, p. 260. Keep, West Coast Shells, p. 89, fig. 75, 1S92. Williamson, 



Proc. U. S. Nat. Mus., Vol. XV, 1892, p. 199. 



Shell large, conical; spire elevated, subacute; whorls six or seven, flat with undulating, 

 nodose keel on anterior margin; transverse ridges on upper part of whorl, with small nodes near 

 middle of shell and toward anterior margin; suture appressed, distinct and wavy; keel prominent on 

 body-whorl; base flat, with faint spiral sculpture; aperture subovate; columellar protuberance on 

 some specimens. 



Dimensions. — Alt. 40 mm.; lat. 45 mm.; defl. 70 degrees. 



This species is characterized by the prominent nodose keel on anterior margin 

 of whorl. Although the living specimens are common, the fossils are rare in this 

 locality. 



Upper San Pedro series of San Pedro and Crawfish George's. Found also in 

 the Pleistocene at Pacific Beach, San Diego. 



Livivg. — Santa Barbara to Cape St. Lucas; Monterey ? (Cooper). 



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

 (Arnold). 



Genus Leptothyra Carpenter. 



Shell small, turbinated, thick; not umbilicated; aperture circular, slightly angulated 

 anteriorly. 



Ty|)c, Lep!(ifJii/rn cnrpcntcri Carpenter. 



