MUSSEES AND PECTENS 33 
There is another mussel, found chiefly in the 
south, concerning which there has been much dis- 
cussion. In West Coast Shells it is called Mytilus 
bifurcatus, Conr., but it seems to have been con- 
founded with another shell of the same name. In 
1898 it was renamed Mytilus stearnsi, Pils. & 
Raym., Stearns’ Mussel, and by this name we 
trust that it will continue to be known. [Extern- 
ally it greatly resembles Figure 15, though it is 
usually considerably smaller. Internally it may 
be distinguished from a Septifer by the absence of 
a deck across the point of the umbo. 
Figure 15 is a good picture of the 
little shell referred to above. Its name is 
Séptifer bifurcatus, Rve., the Branch- 
ribbed Septifer. Its generic name means 
partition-bearer, and was given from the 
iy fact that a little shelly deck is stretched 
across a small part of the interior of 
each valve near the umbo. The shell is 
strong, has a thick, dark epidermis, and is very 
pearly within, where the color varies from white 
to dark purple. Outside, the ribs increase in num- 
ber towards the edge of the shell, sometimes seem- 
ing to actually fork into two. Sometimes the out- 
side is exceedingly eroded and almost all signs of 
ribs disappear, or the surface may become in- 
crusted with foreign substances. The Septifer 
spins a strong byssus and attaches itself to stones, 
where it may dwell in safety. Occasionally a 
specimen is found nearly twice as long as the pic- 
ture. On the whole, this is a very interesting shell, 
and should be sought for, especially in the south. 
Fig. 15 
