154 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
British Marine Testaceous Mollusca, expresses the conviction 
that Modiola and Crenella should be regarded as distinct genera. 
The protoconch, Fig. 10, h, is orbicular, and at the very outset 
the growth of the shell is toward the posterior end, slightly down- 
ward. 
MODIOLA MODIOLUS (Linn^). 
Fig. IL Length, 75 mm. 
By some oversight I have neglected to make a drawing of the 
adult of this species. It is common in rock pools at low tide and 
after storms the shell may be found embedded in the roots of large 
laminarians thrown up on beaches. A young specimen revealed 
the typical characters of Modiola as distinguished from Mytilus. 
Its distinct anal syphon projecting nearly dorsally, the branchial 
Fig. 11. — Modiola modiolus (Linn6). 
syphon formed by the mantle just below the anal opening and 
dropping down on each side, the edges thrown into irregular 
folds are characteristic of all Modiolas and Modiolarias. The 
figure shows the configuration better than any description, and 
is typical of all members of the genus. There was no trace of a 
valve unless the anal syphon represents the structure. 
