LEPIDOPLEURUS. 9 



Color. Grayish-white. 



Size. Length about 12 ram.; breadth 5 mm.; height about 2*5 

 mm. 



Gills. Forming a short posterior row, six or seven in number. 



This species is considerably larger and coarser than the preceding 

 (L. benthus). The tubercles are twice the size and closer together. 

 The shell is also comparatively sharply keeled, instead of having a 

 gently rounded appearance. 



L. BENTHUS Haddon. PI. 1, figs. 1-13. 



Shell. Delicate, brittle, surface with minute inconspicuous short 

 ridges more or less radially disposed, and studded with small tuber- 

 cles. The sides meet at a rounded angle of about 100. Sutural 

 laminae small. 



Anterior valve. With minute scattered tubercles, which pass 

 towards the apex into low tubercular ridges, having a concentric 

 arrangement. 



Intermediate valves. Central areas : The minute surface ridges, 

 when visible, are longitudinally disposed on the jugum, but become 

 radial or oblique on the pleura. The tubercles are round on the 

 jugum, but become somewhat oval on the pleura, and there appear 

 to be concentrically arranged, although in some valves they seem 

 to more or less regularly diverge from the apex. Lateral areas : 

 The surface ridges are radial and more pronounced than elsewhere. 

 On the upper portion of the areas there are transverse low ridges 

 placed further apart than the former ; these ridges by being inter- 

 rupted gradually pass into tubercles. The tubercles are round, 

 distinctly smaller than in the central areas, and more scattered. 



Posterior valve. With a small central umbo. Anterior area : 

 With concentric tubercles, as in the lateral areas. Posterior area : 

 Similar to the anterior valve. 



Girdle. Narrow, with delicate scales, which form a minute fringe 

 at the edge. 



Color. Greenish-white with one or two irregular reddish-brown 

 flecks. 



Size. Length, 8 mm. ; breadth, 3.5 mm. 



Northern Pacific, Lat. 35 41' N., long. 157 42' E., in 2300 fms. 



L. benthus HAD., Chall. Hep. xv, p. 10, t. 1, f. 1, t. 2, f. 1. 



Gills. Seven in number, extending between the prominent anus 

 and postero-lateral angle of the foot. The gill row is one-seventh 



