96 CALIFOKNIA ACADEMY OF SCIENCES. 



Subgenus Nucula s. s. 

 Shell not divaricately sculptured. 

 Nucula ohliqua Lam. is a characteristic species. • 



12. Nucula (Nucula) suprastriata Carpenter. 



Plate XVIII, Fig. 6. 



(f) Nucula tenuis (iion Mont.) Carpenter, Brit. Assn. Rept. 1863, p. 644. Cooper, State Mas. 

 Collection Catalogue. 



Shell small, trigonal, convex, thin, white, pearly interior; umbones turned toward the short 

 posterior end; posterior end sharply rounded, anterior evenly rounded; surface with numerous dis- 

 tinct, rounded, raised, concentric lines; interior of margin finely crenulated; hinge with small, interior 

 cartilage-pit, and numerous sharp teeth on each side. 



Dimensioyis. — Long. 5.8 mm.; alt. 5.2 mm.; diam, 3 mm. 



This beautiful little shell is easily distiugiiishable by its triangular shape, 

 numerous sharp teeth, and distinct concentric sculpture. Specimens identified by 

 Dr. Dall. 



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

 in the upper San Pedro series of San Pedro; common in the upper San Pedro series 

 of Los Cerritos. Found also at Spanish Bight, San Diego. The specimen figured 

 is from the upper San Pedro series at Los Cerritos, and is now in the collection of 

 Delos Arnold. 



(? ) Living. — Straits of Fuca to Santa Barbara; Japan (Cooper). 



Pleistocene. — San Pedro (Arnold): San Diego (Arnold). 



Family VI. LEDID.E. 

 Genus Leda Schinnacher. 



Shell resembling Nucula; oblong, rounded in front, produced and pointed behind; margins 

 even; pallial line with a small sinus; umbonal area with a linear impression joining the anterior 

 adductor. 



Leda j)erniila Mull, is a characteristic species. 



13. Leda fossa Baird. 



Plate XVII, Fig. 7. 



Leda fossa Baird, Proc. Zool. Soc, 1863, p. 71. Carpenter, Brit. Assn. Rept., 1863, p. 644. 

 Dall, Nat. Hist. Soc. British Columbia, Bull, No. 2. 1897, p. 7, PI. II, figs. 3, 13. 



Shell small, elongate, convex, thin; umbones anterior, turning slightly toward the posterior 

 end, which is elongated, narrow and truncated; anterior end short and evenly rounded; sculpture 

 nearly obsolete, a few concentric lines disccrniijle; escutcheon long, narrow, smooth and deep-set; an 

 elongate process on middle of interior of posterior end; hinge witii small internal cartilage-pit, and 

 numerous sharp teeth on each side. 



Dimensions. — Long. 11 mm ; alt. 6 mm ; diam. 3.8 mm.; umbo to posterior end 7.5 mm.; 

 to anterior end 5 mm. 



