— bu shell, and separated by a wide sinus; teeth fairly sharp,» 
ior z 
68 
the pleural and lateral areas, also other olivaceous markings 
are present. . 
Anterior valve.—Unsculptured; under a high power the 
valve is seen to be covered with whitish spots, suggesting 
regular decussation, but the brownish-olive mottling so gener- 
ally covers the valve that in many parts the white spo wei 
indistinguishable. The shell is convex, evenly rounded we 
arched, about twice as broad as long, teeth well defined, wi ^ 
rounded, slightly wavy edges, eaves well developed, teet 
propped or fluted, slits 16, inside whitish and glassy. 
Posterior valve.—Unusually broad for this valve, Meum 
only slightly less broad than the median valves, mucro mia) 
anterior, posterior slope evenly rounded but steep, convex. 
ridge divides the portions, starting at the mucro pisei A 
diagonally to the suture. Behind the mucro is another 
edged, and are fluted or propped on the inside as in the 
anterior valves, eaves distinct. de. 
Median valves.—Uniformly smooth, glossy, diee 
tured ; the anterior margin of the lateral area is slight d M dol 
in some of the valves, especially in valve 2. e pns pori 
barely distinguishable, but is slightly raised and flat A agentes 
Under a low power ateral, wavy, longitudinal, a di ad 
bands are easily seen; one valve has six of these ym 
either side. When disarticulated and cleaned and — : 
a high power some additional markings are reveale tici = 
dorsal and pleural areas are very distinct from the 
dove peciall 
fo discover any rising in the shell. In some lights, especia iy 
.. daylight, the white interspaces look like white spots wo 
Olivaceous markings like interspaces. The we ru of 
are large, produced to about half the width (longitu 
te de n ‘rounded as in the anterior and posterior valves, and J can 
