CRETACEOUS FOSSILS. 177 



C. AL.EFORMLS, 11. 8. 

 PI. 29, Fig. 63. 



Shell large, broadly rounded in advance, narrow, produced, 

 and truncated behind; beaks about a third of the length from 

 the anterior end, high; posterior cardinal margin nearly straight, 

 bordered by a broad, deep groove, extending from the beaks to 

 the posterior end; base prominently and broadly rounded in the 

 middle, sinuous behind. Surface marked by small, regular, con- 

 centric ribs. 



Figure, natural size. 



From a bed intermediate in age between tbe Martinez and Tejon Groups, near 

 Lower Lake village, Lake County. 



The largest of our Californian Corbulas,' and characterized by its narrow pro- 

 duced posterior end. 



ANATINA, Lam. 



A. QUADRATA, 11. S. 

 PI. 29, Fig. 64. 



Shell moderate in size, subquadrate; beaks nearly central; 

 length and width about as eight to five ; anterior end gaping, 

 truncated, and with the corners rounded; posterior end convexly 

 subtruncated, or rounded ; base nearly straight, being a very 

 slight curve, most prominent in the middle; the cardinal margin 

 is slightly excavated in advance of the beaks, and sloping and 

 nearly straight posteriorly. Surface marked by a few lines of 

 growth. 



Length, 2. inches ; width, 1.25 inch. 



From the greenish rock on the north shore of Departure Bay, Nanaimo, Van- 

 couver Island ; associated with Pccten Traskii, Trigonia Evansana, and other 

 species characteristic of the Chico Group in California. 



Of somewhat the style of A. lata, but longer and more regularly quadrate ; from 

 A. Tryoniana it can be distinguished by being shorter, the ends being more dis- 

 tinctly truncated, and by its wanting the angular ridge descending from the beaks; 

 from A. incequilateralis it can be known by the more central position of the beaks, 

 and the less rounded ends. 



PAL. VOL. II. — 24 



