MOLLUSCA. 417 



the individual teeth on each side are slightly oblique to the inner 

 margin of the hinge-plate, the anterior and posterior rows are 

 nearly straight or slightly convex, meeting beneath the beak in 

 a rounded angle. Both muscular impressions moderately de- 

 veloped. The external surface of the shell, as indicated by im- 

 pressions, is marked by fine, regular, radiating costae, and by 

 more or less irregular concentric lines of growth. The beaks 

 are approximate and the cardinal areas small. 



Remarks. This species is very similar to A. subaustralis, but 

 may be distinguished from it by its much smaller teeth which are 

 arranged in a broadly /\ -shaped hinge with the angle under the 

 beak rounded, instead of in a broadly arcuate line. Another dis- 

 tinction is found in the almost or wholly obsolete crenulations 

 upon the interior of the free margins of the valves. 



Formation and locality. Wenonah sand, near Crawfords 

 Corner (i26 3 ). 



Geographic distribution. New Jersey. 



Axinea compressa n. sp. 

 Plate XXXV., Fig. 9. 



Description. Shell subcircular, the valves compressed, oblique, 

 the height of the type specimen 23 mm., its length about 25 mm., 

 its convexity -4 mm. The anterior margin from the beak to the 

 middle of the basal margin forms nearly a semicircle, the pos- 

 terior margin is obliquely subtruncate above from the beak nearly 

 to the middle of the shell, below which point it rounds into the 

 basal margin. In the internal casts the free margin is strongly 

 crenate ; the beaks pointed, the lateral slopes meeting in an angle 

 of about 90; impression of the hinge-plate rather broad, with 

 10 or more rather strong teeth visible on each side of the beak, 

 the teeth are placed a little obliquely to the inner margin of the 

 hinge-plate, the anterior row is slightly arcuate, the posterior row 

 nearly straight. The posterior muscular impression is slightly 

 defined, the anterior one scarcely recognizable. The external 

 surface of the shell, as indicated by an impression, is marked 

 only with concentric lines of growth. 

 27 PAI, 



