176 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
section would resemble the figure 8, so deep is the line. The 
branchial syphon is one and a half times wider than the anal 
syphon. The color is light salmon mottled with lighter spots. 
The opening of the branchial syphon is fringed with from twenty 
to twenty-four papillae of nearly uniform size, a few bifurcated. 
The valve is of extreme tenuity and only projects slight^ beyond 
the edge of the anal syphon; a few papillae wide apart encircle 
its base. Verrill, in describing the syphons of the species says, 
"The orifices are simple without apparent papillae." He must 
have examined a single specimen in which the ends of the syphons 
may have been bitten off by a fish, but as will be seen by my 
figures his statement is erroneous. The papillae are very dis- 
tinct; the valve, however, is short and extremely delicate. The 
usual attitude of the syphons is to turn dorsally. The mantle 
projects from the edge of the shell like a curtain. In the few 
figures of fringed mantles in Forbes and Hanley, the draughtsman 
has drawn from memory a line of uniform scallops. To obtain 
a clear idea of the true appearance of these tissues every curve 
and notch must be accurately copied. In the drawing here 
given this has been done. Just below the base of the branchial 
syphon the mantle projects either as a flattened ribbon with 
slightly digitated end, or as a leaf-like expansion, the edge 
minutely digitated. This extends twice as far as the usual 
boundary of the mantle folds. A similar feature is seen in Venus 
mercenaria. I have never observed the foot obtrude. 
VENUS MERCENARIA Linn6. 
Fig. 31. Length, 70 mm. 
The mantle is fringed but with more uniformity than that of 
Cytherea convexa. It is light salmon color. At its junction with 
the branchial syphon it shows rather larger digitations; viewed 
from below the folds of the mantle appear very close together 
and interlock. Foot short and broad, occupying nearly the 
entire length of the ventral margin of the shell. The syphons 
are united, are very short, and of nearly equal diameter, the 
branchial syphon being larger. The margins of the openings 
are fringed with very small papillae crowded together; these 
vary slightly in length, a few being bifurcated. The anal 
papillae alternate long and short, the branchial papillae not 
