644 JAMES L. KELLOGG 
tion of the adductor muscles, is discharged through the incurrent 
siphon. It does not appear to be discharged between the mantle 
folds below the siphon, as in Mactra and other forms. 
Chione fluctifraga 
This form was studied at San Diego Bay, California. 
Gills. Cilia streams are to the margin on all lamellae. There 
is a forwardly directed tract between demibranchs, at their 
bases, but apparently none at the bases of outer lamella of the 
outer, and inner lamella of the inner demibranchs. The inner 
demibranch is attached anteriorly to the inner face of the pos- 
terior palp, and very close to the lateral oral groove. 
Palps. ‘The palp ciliation is like that of Schizotherus, except 
that no dorsally directed currents were seen on the faces of the 
folds (fig. 5). Though the folds are minute, currents directed 
downward to the ventral margin in the grooves between them, 
were clearly demonstrated by the use of heavy, powdered sand. 
Visceral mass. The ciliation here (fig. 5, vms) is downward 
and backward, collections being cast from the posterior wall as 
in Venus. 
Mantle. Figure 6 shows a ciliation like that of Venus. 
Chione succincta 
The ciliation of all organs is like that of C. fluctifraga. 
Tivela crassatelloides Conrad 
The Tivelas are found in California from Santa Cruz south- 
ward. They are very abundant at Pizmo Beach, and in the 
market are known as the Pizmo clams. The shell valves are 
extremely heavy. The ciliation of all organs seems to be pre- 
cisely like that of Venus. There is a small siphon membrane, 
but no waste canal on the mantle. The usual line through the 
general ciliation of the mantle, found in forms related to Venus, 
is well defined. The tentacles of the mantle margins are tree- 
like, bearing secondary and tertiary branches. 
