MORSE: OBSERVATIONS ON LAMELLIBRANCHS. 
153 
MYTILUS EDULIS I.inn6. 
Fig. 10. IvOHRth, 82 mm. 
The anal syphon shows as a short tube just Ijoyond the edge 
of the shell and projects from the posterior dorsal region. 
Below this the mantle is wide open; there is no constriction 
indicating a l)ranchial syphon. The mantle is bordered with 
large papillae and these are strongly fimbriated at the branchial 
region, becoming less so toward the anterior end. The color is 
light brown. Meyer and Mobius in their work (Fauna der 
Kieler Bucht) give beautiful colored plates of certain moUusks 
and among these figures is Mytilus edulis. The fimbriated 
fringes are carefully figured with broad bases showing leaf-like 
papillae. In our mussels the bases are narrow as shown in Fig. 
^ 
i^Ai^i> 
Fio. 10. — Mytilus edulis Linn6. 
10, a. I may add in this connection that in our Margaritana 
margaritifera, at least from Maine, the mantle is fringed with 
fimbriated papillae as in Mijtilus edulis. I have searched in 
vain European descriptions of what was always supposed to be 
the same species and no reference is made to these digitated 
papillae lining the mantle. The species is circumpolar and in 
crossing Yezo I found in a river apparently the same mussel. 
William Stimpson, in his Shells of New England, says, "I have 
arrived at the conclusion that the genera Modiola, Crenella, 
Modiolaria, etc., should be reunited to Mytilus, since I have found 
as great differences between the species of these sub-genera as 
among the sub-genera themselves." William Clark, author of 
