1917.] NATURAL SCIENCES OF PHILADELPHIA. 189 



full and prominent, curving well forward, at about the anterior 

 fourth of the hinge line. Sculpture of 25 ribs, those of the left 

 valve all closely granose, the grains rounded on the convexity, 

 transverse towards the lower margin. Intervals sharply and finely 

 striate transversely. On the anterior end the ribs are wider and more 

 spaced. The right valve is similar except that it is very slightly 

 smaller, and the granulation is weaker on and near the posterior 

 ridge. Cardinal area is rather wide, with several concentric angulated 

 grooves. Hinge line is rather short, with about 44 teeth. 



Length 20.5, alt. 19.5, diam. 19 mm. 



" 23.5, " 22, " of left valve 12 mm. 



Type No. 2734, A. N. S. P. 



This prettily sculptured species, known from numerous specimens, 

 stands near A. santarosana Dall, but it differs by the smaller number 

 of ribs, the anterior ones not being mesially grooved. Area alcima 

 Dall of the Pliocene has more ribs. In A. rhomhea Hanley, A. chem- 

 nitzi Phil, and A. piUieri Dall, of the Pleistocene and recent faunas, 

 the beaks turn forward less than in A. coccopleura. 

 Area tolepia saxea n. subsp. 



The shell is decidedly narrower than A. tolepia, but with sub- 

 stantially the same sculpture; 33 ribs. 



Length 31, alt. 24, diam. 23.3 mm. 



Type No. 2742, A. N. S. P. 



It is less abundant in the collection than A. tolepia. 



Area tolepia scapularis n. subsp. 



The posterior end is straightened, angular and somewhat produced 

 above, subangular below, 33 ribs. 



Length 29, alt. 22.5, diam. 21 mm. 



Type No. 2739, A. N. S. P. • 



Area tolepia erassicardinis n. subsp. 



Similar to the typical form except that the hinge is very thick, 

 32 ribs. 



Length 30, alt. 27, diam. 26 mm. 



T\T3e No. 2747, A. N. S. P. 



Area cyclica n. sp. 



Shell subcircular, plump, very thick, equivalve, with rather 

 prominent nearly contiguous beaks at the anterior third of the length. 

 Cardinal area extremely narrow behind the beaks, short but broader 

 and triangular in front, with about two grooves. Posterior end 

 broader than the anterior, an angle at its junction with the hinge 



