1922 ] Packard: New Species from Santa Ana Mountains 419 



TRIGONARCA SECTILIS, n. sp. 

 Plate 27, figures la, lb, and lc 



Type specimen 12316, Coll. Invert. Palae., Univ. Calif., loc. 2144. 



Shell small, trigonal, inequilateral, ventricose, the diameter being nearly 

 equal to length. Anterior extremity short, evenly rounded. Posterior dorsal 

 side of the shell conspicuously flattened; basal margin nearly straight. Beaks 

 small, widely separated. Posterior umbonal ridge sharply marked, extending 

 to the bluntly pointed posterior extremity. The margins of the shell within 

 this area pout, forming the boundary of a groove which extends from the beaks 

 to the ventral margin. Five oblique anterior teeth, and apparently about the 

 same number of posterior teeth on hinge of cotype. The teeth short, and trans- 

 verse on the middle portion of the plate. Length of type, 43 mm.; height, 

 45 mm.; diameter, 40 mm. 



This odd-shaped mollusk is represented by a number of specimens 

 from localities within the Actaeonella oviformis zone. It is also found 

 among the collections from northern California belonging to the Uni- 

 versity of Oregon. 



Horizon. — Chico group, Actaeonella oviformis zone. 



Family Limopsidae 

 Genus LIMOPSIS Sasso 

 LIMOPSIS SILVERADOENSIS, n. sp. 

 Plate 27, figures 2 and 4 



Type specimen 12324, Coll. Invert. Palae., Univ. Calif., loc. 2143. 



Shell small, thin, tumid, higher than long; nearly equilateral. Anterior 

 dorsal margin slightly concave beneath the beaks; posterior margin convex, 

 meeting the narrow base with an even curve; margins flattened. Umbones 

 prominent, beaks pointed. Surface of shell apparently smooth; hinge of cotype 

 edentulous, with a V-shaped ligamental pit and 5 to 7 denticulations occurring 

 on both sides of the beak, on a low ridge extending ventrally as two curved 

 lines which meet in a broad curve at a point about two-thirds of the distance 

 from the beak to the base. Length of type, about 1,5 mm.; height, 17 mm.; 

 convexity, 3 mm. 



Horizon. — Chico group, Actaeonella oviformis zone. 



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