152 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
Type. Antigona lamellaris Schumacher, 1817. 
Distribution. World-wide. 
Range in Time. Oolite, Pleistocene. 
SECTION VENTRICOLA Roemer, 1857. 
Antigona fordi Yates, 1890. 
Plate 55, fig. 3. 
Santa Barbara Soc. Nat. Hist., Bull., 2:46; pi. 1, figs. 1-5. 
Shell thick, solid, ovate, tumid, truncated at point, exterior light brown; 
beaks projecting to front of the shell, much elevated and curved, making 
more than half a turn forward and inward; lunule rough, much de¬ 
pressed, heart-shaped, bounded by an impressed line; ligament not large, 
but nearly hidden in the depression between the elevated beaks; surface 
with concentric rounded ridges and grooves, marked on the surface by 
minute concentric laminre, about one-third of a millimeter apart, forming 
a chalky covering to the shell; the entire surface of the shell is further 
marked by fine, but somewhat irregular radiating lines and corresponding 
depressions a little less than a millimeter apart; these lines are more 
distinctly shown on the anterior portion of the shell; margins finely 
crenulated; young shells are of a dirty yellowish white, and mature shells 
which have become divested of the chalky exterior are of a yellowish 
brown color, and together with the young shells are marked with four 
radiating rows of chocolate colored blotches. Length, 2^; height, ; 
diameter, 2 inches. (Yates.) 
Type locality, Santa Barbara, California. 
Range. Monterey, California, to Lower California. Panama. 
Genus SAXIDOMUS Conrad, 1837. 
Shell equivalve, gaping posteriorly; hinge with from four to five com¬ 
pressed cardinal teeth in the right valve; in the left valve, four; muscular 
impressions two, large, rounded; pallial impression with a profound sinus. 
Type. Saxidonms mittallii Conrad. 
Distribution. California. 
Range in time. Pleistocene, Pliocene, Miocene. 
Saxidomus nuttallii Conrad, 1837. 
Plate 35, fig. 2. 
Jour. Acad. Nat. Sci. Phila., 7:249; pi. 19, fig. 12. 
Shell suboval, disk rough, with concentric striie, elevated on the pos¬ 
terior slope; posterior extremity truncated; color white, with brown spots 
and stripes about the umbo and ligament. Length, 2 inches. (Conrad.) 
Type in Acad. Nat. Sci. Phila. Type locality, San Diego, California. 
Range. Bolinas Bay to San Diego, California. 
