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University of California Publications in Geology [ VoL - 13 



Genus ANTIGONA Schumacher 

 ANTIGONA WILLISI, n. sp. 

 Plate 5, figures 2a and 26 

 Type— No. 12379, Univ. Calif. Mus. Pal. 



Shell elongate, subovate; lunule large, well defined, and depressed; escutcheon 

 elongate, depressed, and well developed in left valve and apparently absent in 

 right; anterior dorsal margin gently concave and about three-fifths the length 

 of the posterior, which is almost straight; posterior end subacutely rounded; 

 anterior end produced and broadly rounded; surface of shell sculptured by 

 regular undulations; near the beak and over a large part of the surface, undula- 

 tions about equal in size to interspaces, but near ventral margin become much 

 more closely crowded; undulations and interspaces marked with fine incremental 

 lines; hinge unknown. The species is quite distinct because of its elongate 

 form. 



Dimensions. — Type specimen U. C. no. 12379; alt., 33.3 mm.; width, 42.7 mm.; 

 greatest diameter, 22.8 mm. 



Occurrence. — Briones formation, IT. C. loc. no. 146. 



Named in honor of Professor Bailey Willis, Stanford University. 



Family Mactridae 

 Genus SPISULA Gray 

 SPISULA FALCATA BRIONIANA, n. var. 

 Plate 4, figures 2a and 2b 

 Type— No. 12380, Univ. Calif. Mus. Pal. 



Shell small to medium in size, subtrigonal, inequilateral, equivalve; beaks 

 rather inconspicuous, incurved and only slightly prosogyrous; anterior dorsal 

 edge long and straight; posterior dorsal edge straight to gently convex, and about 

 two-thirds the length of the anterior dorsal edge; posterior end evenly rounded; 

 anterior ventral end produced and subacutely rounded; surface smooth except 

 for fine incremental lines; hinge pdate short, resilifer shallow; cardinals small 

 and fragile; laterals very short and close to laminae. 



Dimensions. — Type specimen U. C. no. 12380; alt., 17.6 mm.; length, 24.0 mm. 



Occurrence. — Briones formation. Type from U. C. loc. no. 3522. 



This variety resembles 8. falcata (Gould), 25 a recent species of the 

 West Coast, but it differs from the latter in that it is higher in pro- 

 portion to length ; it possesses a more prominent umbonal ridge ; it has 

 a shorter hinge plate and shorter laterals ; and the distance from the 

 center of the hinge plate to the distal ends of the laterals is about 

 one-half of what it is in 8. falcata. 



25 Gould, Proe. Brit. Soc. Nat. Hist., vol. Ill, p. 216, 1850. 



