ARNOLD] FOSSIL MOLLUSKS FROM CALIFORNIA 437 



Locality. — Alcatraz asphalt mine, near Sisquoc, Santa Barbara 

 County, California; locality No. 4471. 



Horizon. — Fernando formation, lower Pliocene portion. 



SPISULA CATILLIFORMIS Conrad, var. ALCATRAZENSIS, new 



variety 



PI. LVI, fig. 6 



Description. — Shell averaging about 130 millimeters in longi- 

 tude, oval in outline, slightly narrower in front than behind, equi- 

 valve, inequilateral, ventricose, extremities slightly gaping; base 

 regularly arcuate ; posterior portion of dorsal margin nearly straight 

 at umbo, gradually becoming more and more arcuate as it passes 

 around the broadly rounded extremity ; anterior dorsal margin only 

 slightly depressed in front of umbo, but carrying a slight bump only 

 a short distance from the latter; anterior extremity more truncate 

 and narrower than posterior; beaks slightly anterior, bent forward, 

 but not exceptionally prominent. Surface consists of numerous 

 more or less irregular lines of growth. Hinge and interior quite 

 similar to typical form. 



Dimensions. — Longitude, 128 mm.; altitude, 98 mm.; diameter, 

 57 mm. 



Notes. — This variety is more ventricose, more excavated and 

 attenuate in front, more regularly rounded below, and has the beaks 

 more central than the typical S. catilliformis. Named for type local- 

 ity, Alcatraz asphalt mine. 



Type.— Cat. No. 165,291, U. S. N. M. 



Locality. — Alcatraz asphalt mine, near Sisquoc, Santa Barbara 

 County, California; locality No. 4471. 



Horizon. — Fernando formation, lower Pliocene portion. 



SPISULA SISQUOCENSIS, new species 



PI. LVI, fig. 1 



Description.— Shell averaging about 120 millimeters in longi- 

 tude, subtrigonal in outline, equivalve, inequilateral, ventricose ; base 

 regularly arcuate; beaks anterior, prominent, bent forward, pro- 

 truding beyond periphery or shell ; anterior end shorter and nar- 

 rower than posterior, which is evenly rounded; area in front of 

 beaks depressed concavely as a whole, but slightly elevated at mar- 

 gin, this condition, when the two valves are together, suggesting a 

 large lunule with a slightly raised ridge running down the middle; 

 posterior margin becomes more and more arcuate as extremity is 



