OF CONCHOLOGY. 199 



DESCRIPTIONS OF NEW TERTIARY FOSSILS, WITH NOTES 

 ON TWO OENERA OP LAMELLIBRANCHIATA. 



BY T. A. CONRAD. 



MACOMA, Leach. 

 M. SUBLINTEA, Conrad. PI. 11, fig. 5. 



Suboval or subtriangular, inequilateral, compressed ; anterior 

 side shorter than the posterior, subcuneiform ; posterior dorsal 

 margin slightly curved, oblique, regularly rounded at the ex- 

 tremity ; ventral margin slightly curved ; disk with minute con- 

 centric slightly impressed lines. 



Locality. Vicksburg. Oligocene. 



ABRA, Leach. 

 A. PROTEXTA, Conrad. Plate 11, fig. 4. 



Elliptical, elongated, inequilateral, compressed, sinuous ; disk 

 widely contracted. 



Locality. Vicksburg. Oligocene. 



Of this species one valve, the left, is all that I have seen. It 

 is remarkable for its length. 



AXIN^A. 

 A. BELLA, Conrad. Plate 13, fig-. 1. 



Subovate, convex, equilateral ; ornamented with fine, close, 

 regular concentric lines ; ribs prominent, acute and entire on 

 the umbo and thence dividing into two, and sometimes three, 

 narrow ribs ; interstices with each a rib, and sometimes one or 

 two lines, all which disappear on the umbo ; marginal teeth nar- 

 row, numerous, closely-arranged ; hinge series in two subequal 

 continuous curves. 



Locality. Day's Point, Virg. Miocene, 



Among recent species the nearest approach to the bella is A. 

 parcipicta, Reeve. Monog. fig. 14. 



