ARNOLD— THE PALEONTOLOGY AND STRATIORAPHY OF SAN PEDRO. 139 



71. Cardium (Trachycardium) quadrigenarium Conrad. 



Cardium quadrigeyiarmm CoN., Jour. Phil. Acad. -Sci., Vol. VII, 1837, p. 230, PI. XVII, fig. 5; 

 ^ bdeolabrmn Gi.n. (/7(/ir Carpenter, Brit. Assn. Rept., 1863, p. 642). Cooper, 7th 

 Ann. Rept. Cal. St. Min., 1S88, page 232. Keep, West Coa.st Shells, p. 192, 1892. 

 Williamson, Proc. U. S. Nat. Mus., Vol. XV, 1892, p. 190. Dall, Trans. Wagner 

 Inst. Sci., Vol. Ill, Part. 5, 1900, p. 1091. 



Shell large, oval, ventricose, thick; umbones central, prominent, turned only slightly an- 

 teriorly; surface sculptured with about forty prominent, subangular, smooth, radiating ridges, which 

 are roughened by prominent pointed tubercles on their posterior angle; those ridges near the pos- 

 terior margin are less prominent, but are nodose for nearly their whole length; teeth and interior as 

 in C. corbis; margin sharply serrated. 



Dimensions. — Long. 105 mm.: all, 105 mm.; diam. 86 mm. 



Distiiigiii.shable by large .size aiul tuberculated ridges. Specimens identified 

 l)y Dr. Dall. 



Found in the upper San Pedro series of San Pedro, Los Cerritos and tlie 

 Long Eeacli bhiff. Found also in the Pleistocene of Twenty-sixth Street and Pacific 

 Beach, San Diego. 



Living. — Monterey to San Diego (Cooper). 



Pleiatocene. — San Pedro (Arnold): San i)iego (Cooper; Arnold). 



Pliocene. — Calleguas Ranch, Ventura County (Cooper). 



Subgenus Ringicardium Fischer. 



Shell rotund, gaping, with flat ribs and channels, the posterior area with granulose channels; 

 posterior margin sharply spinose, the spines crossing each other over the gap; left cardinals when 

 interlocked posterior to the right ones. 



Type, Cardium ringens (Gmel.). 



72. Cardium (Ringicardium) procerum Soverhij. 



Plate XV, Fig. 6. 



Cardium procerum Sby., Carpenter, Brit. Assn. Rept., 1863, p. 620. Dall, Trans. Wagner Inst. 



Sci., Vol. Ill, Part 5, 1900, p. 1091. 

 Cardium pana7nense , not of Snv., of Cooper, 7th Ann. Rept. Cal. St. Min., 1888, p. 232. 



Shell of medium size, suboval, of medium thickness, ventricose^ with a rather angular 

 appearance at about one-fourth the length from the anterior margin; surface sculjitured by aliout 22 

 subangular, smooth radiating ridges, with narrow, canel-like grooves between; each valve with 

 three very prominent sharp teeth; margin sharply serrate. 



Dimensions — Long, i mm.; alt. 23 mm.; diam. 19 mm. 



Distinguishable by angular appearance near anterior side, and by the com- 

 paratively small number of smooth radiating ridges. Specimens identified by Dr. Dall. 



Rather common in the upper San Pedro series of San Pedro, Long Beach and 

 Los Cerritos; one specimen from the lower San Pedro series of Deadnian Island. 'Y\\e 

 specimen figured is from the upper San Pedro series at San Pedro, and is now in the 



