186 PEOCEEDINGS OF THE ACADEMY OF [Feb., 



radial ribs predominate at each end, while the concentric sculpture 

 is strongest in the middle of the valve. Anteriorly the first eight 

 radial ribs are prominent and densely granulose ; the median por- 

 tions of the valves are regularly concentrically costate and radially 

 ribbed, with finer closely packed costre prominent in the interstices; 

 the concentric costie are cut into even gi*anules by the crossing 

 radial costaj ; at the posterior angle of the valve there are about 

 five or six prominent heavy squamose radial ribs; from this point 

 the radial ribs predominate, and gradually become finer to the pos- 

 terior margin. Beaks prominent, directed forward, smooth, 

 except a few concentric growth lines. Lunule impressed, a little 

 convex, narrow, about one-fourth the length of ihe shell, generally 

 of a darker color than the rest of the shell and provided with six 

 or eight longitudinal granulose ribs. The groove of the ligament 

 is linear, tapering at the extremities. The margin is dorsally quite 

 evenly arcuate; rounded anteriorly, a trifle convex at the lunule; 

 evenly arcuate ventrally; posterior obliquely truncate, with a very 

 blunt obtuse angle near the centre. The margin is very finely 

 crenulate; beginning at the anterior side of the beak it is minutely 

 crenulate along the edge of the lunule, becoming coarser ven- 

 trally, then gradually becoming finer, and ends abruptly at the 

 posterior end of the ligament. The hinge is broad under the con- 

 vex lunule, narrower posteriorly, with three teeth in each valve. 

 The right valve has the anterior tooth small, lamellar and nearly 

 parallel with lunule; the middle tooth is triangular and directed 

 forward, its posterior ejid is nearly vertical, while the anterior end 

 is oblique and almost parallel to the antei'ior tooth; posterior tooth 

 large, about the size of the triangular central, slightly bifid or 

 grooved at the summit, directed backward. The left valve is three- 

 toothed, anterior tooth lamellar, higher than the rest, directed 

 forward; central nearly lamellar, vertical, with a bifid or grooved 

 summit; posterior small, lamellar, directed obliquely backward, 

 with a pointed summit. The adductor muscle scars of nearly 

 equal size, palhal line evenly arched, with a moderately deep pallial 

 sinus. Alt. 15, diam. 21, diara. 9 mm. 



Locality. — In ballast from South Africa. 

 ' Types in collection of the Academy of Natural Sciences of Phila- 

 delphia, No. 79,395, collected by Mr. J. G. Malone. 



This species diflfers from V. squamosa Linn, by being smaller 



