OTHER BIVALVE’ MOLLUSKS 97 
the last species, and the pallial sinus is smaller. 
Spisula falcata, Gld., the Faleate Mactra (Stan- 
della faleata), has a shell of moderate size, resem- 
bling Mactra californica, but it has a smaller sinus 
and a narrower anterior end. The shell is glossy, 
thin, and rather flat. It is found in British Colum- 
bia, but extends far southward. 
Labiosa (Reta) undulata, Gld., the Wavy Reta, 
is a very distinct, though rather rare southern spe- 
cies. The hinge resembles that of the Mactras and 
shows the triangular pit plainly. The outline is 
not very different from Figure 85, but the shell 
is very thin, not merely at the edges but through- 
out its whole extent, and is very decidedly marked 
with concentric ridges, which even appear on the 
inner surface. Near the beaks it is much inflated. 
Externally it is hght brown or ashy, and when at 
all thickened the interior is white. Three or four 
inches is the common length. 
The last member of this group has the largest 
shell of all, sometimes reaching a remarkable 
length, while specimens of six inches are not un- 
common. Its name is 7'résus nuttalla, Conr., the 
Washington Clam, (Schizotherus n.). This huge 
clam burrows deeply in the mud, and is therefore 
rather hard to capture. It makes an excellent 
chowder, and a very few clams are enough for a 
large family. 
The shell is oblong, bulged, rather thin, and it 
gapes widely at the end where the long siphons 
