182 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
and the beak comes nearer the vertical center of the shell which 
is more delicate. 
On what ground these two closely allied species were separated 
into distinct genera it is difficult to conceive. They both have 
the ligament distinctly external. T. tenera is more polished than 
T. tenta, the dentition of the shell seems less developed than 
that of T. tenera. The shell has the same tendency to bend 
laterally at the syphonal end as in so many of the Tellinas. 
T. tenera is much more common than T. tenta. If that constitutes 
a generic distinction the taxonomists are welcome to it ! 
MACOMA FUSCA Say. 
Fig. 36. Length, 26 mm. 
The members of the Tellinidae, among which should be in- 
cluded Cumingia as Stimpson suggested seventy years ago, are 
remarkable for the length and mobility of their syphons, which 
are sharply separated and terminate in a six-notch opening. In 
Macoma fiisca the openings of the syphons are deeply notched 
and the openings are identical. Faint lines run along the syphons 
from the beaks of each notch. In expansion the anal syphon 
appears first and curves dorsally, the branchial one stands 
straight out and is very mobile, moving rapidly about and 
sucking up dirt and stuff from the bottom of the dish in which 
it is confined, in this action pushing hard against the surface 
sufficient to turn the shell and make a large clean area about it. 
It is opaque and yellowish in color. The anal syphon is translu- 
cent; no valve was observed. The edge of the mantle protrudes 
sHghtly beyond the edge of the shell around its whole circum- 
ference, more at the posterior end. It is fringed throughout 
with small papillae, a few of which are bifurcated. The cruciform 
muscles are near the posterior end. The foot is large and active 
in movement. The faeces are discharged in the shape of flat- 
tened disks with square edges, like checkers; sometimes a few 
adhere in a row. These disks to the number of thirty-eight 
were rapidly expelled. On October 19 the creature was filled 
with eggs. 
