484 University of California Publications in Geology [Vol. 9 



dorsal margin straight with moderate slope ; the posterior dorsal 

 margin slightly concave with a gentle slope to a narrowly rounded 

 rostrum ; posterior end, narrowly rounded ; ventral margin, broadly 

 convex. Very fine growth lines decorate the shell. 



This species is larger, its rostrum is less pointed and its ribbing 

 much finer than L. gabbi Conrad. 



Dimensions. — Height of broken specimen, the type, 13 mm. ; 

 length, 22 mm. 



Occurrence. — University of California Locality 1817. 



LUCINA PACKI, n. sp. 

 Plate 36, figure 12 



Shell small, subcircular in outline; posterior dorsal margin 

 straight with moderate slope to a subtruncate posterior ; beak sub- 

 central, rounded, prominent; decoration consisting of very fine sharp 

 concentric lines of growth. 



Named for Robert Pack, Palaeontologist, U. S. Geological Survey. 



Dimensions. — Length, 8.5 mm. ; height, 8 mm. 



Occurrence. — Type is from University of California Locality 672. 



LUCINA DIEGOENSIS, a. sp. 

 Plate 37, figures la, lb 



Shell medium in size, orbicular, thick, witli central prominent 

 beaks. Lunule wide, short, and very prominent ; escutcheon long, nar- 

 row ; anterior dorsal margin markedly concave under the beaks ; the 

 slightly convex posterior dorsal margin slopes with moderate angle 

 to a truncated posterior end ; ventral margin nearly semi-circular ; 

 right and left valves equal. The surface is marked by strong, sharp 

 concentric incremental lines and by a feebly developed umbonal 

 groove which extends to the middle of the posterior extremity. 



This species is thicker than L. annulatus or L. acutilineatus and it 

 differs from both in the greater slope of its posterior dorsal margin. 



Dimensions. — Height, 29 mm.; length, 32 mm.; thickness of two 

 valves, 16 mm. 



Occurrence. — University of California Locality 2226, Tejon of 

 Rose Canon, San Diego County, California. 



MARCIA ( ?) CONRADI, n. sp. 

 Plate 38, figure 3 



Shell small, ovate, thick, with thin shell substance ; beak located 

 one-third the distance from anterior end, rounded and prominent; 



