112 BULLETIN 60, UNITED STATES NATIONAL MUSEUM. 



terg'al area has sculpture of wide, flat, transverse ribs parted b}^ 

 narrow grooves. The scutal area has pleats at right angles to those 

 of the other area. There is a radial depression near the upper margin, 

 and a weak elevation, hardly to be called a rib, near the lower diag- 

 onal rib. 



The fixed scutum is irregularly subtriangular, with the apex curved 

 strongly toward the tergum, not projecting; its surface, is divided into 

 three areas: the median area widest, flat, with sculpture of very wide, 

 flat pleats, weakh^, irregularly striate parallel to the pleats; the rostral 

 area is narrow, forming part of the rostral wall, sculptured with pleats 

 deeper than those of the median area and at right angles to them; the 

 tergal area is very narrow, not reaching to the base, obliquel}^ pleated, 

 and separated from the median area by a ledge, being depressed below 

 the level of the latter. 



The fixed tergum has two faces nearly at right angles, and is divided 

 into three areas: the scutal area is triangular, does not reach the base, 

 and is sculptured with vertical pleats; a deep, narrow furrow separates 

 it from the median area. The median area has sculpture of wide, flat 

 pleats, which are angulate or V-shaped except near the apex, where 

 they are close and straight. The carinal area has obli(|ue pleats, 

 sinuated where they pass over the rounded rib at the occludent margin. 



The carina is quadrangular, with parallel tergal and basal margins, 

 its surface divided by a weak diagonal groove into two triangular 

 areas. The lower area has weak sculpture of widely spaced grooves 

 parallel to the basal margin. The rostral area has a strong, narrow 

 ril) along the upper margin, followed l^y a deep furrow. Below this 

 there are weak indications of two wide radial ribs, indicated more by 

 the curvature of the pleats running over them than by actual elevation 

 of the ribs themselves. The umbo projects a little. 



The rostrum is quadrangular with slightly projecting umbo. It has 

 two curved, radial articular ridges, the upper one strong, the lower 

 low and wide. Above the upper rib there is a narrow excavated area 

 forming a ledge along the base of the movable scutum. In this area 

 there are a few weak radiating rib lets. 



Greatest carino-rostral length, 11 mm. ; greatest breadth, 6 mm. ; 

 height from base to apex of the fixed tergum, 8.7 mm. 



The high, compressed shape, wide, pleat-like sculpture, and steepl}'^ 

 sloping movable valves, with onl}^ one or two articular ridges, are char- 

 acteristic features. It is closely related to V. oiitida Hoek, from the 

 Moluccas; but it difi'ers by being twice the size of that species, with 

 the suture uniting rostrum and carina coarsely zigzag, with three 

 major projections on the carina and two on the rostrum. In V. uitida 

 there is a single strong upper tooth, the suture below it being straight. 



There are two specimens, the type and another taken with it. The 

 latter (Plate X, fig. 8) is shorter and wider than the type. The mov- 



