PLATE X30. 
Mytilus Modiolus is the largest species of this genus that inhabits the 
British shores ; being from six to seven inches in length, and three in 
breadth. It is a strong and heavy shell ; the outside is of a blackish 
tolour inclining to purple. It is covered with a thin filmy brown 
epidermis, and often with balani and other remains of crustaceous 
animals. Within, it is smooth and pearly, and sometimes richly - 
coloured with a variety of vivid hues, in which red, purple and green 
chiefly predominate. These shells lie only in deep waters, and are 
never cast upon shore; but sometimes they seize the bait of the 
ground lines, and are hauled up by the fishermen, 
.Da Costa received the M. Modiolus, of a fmall size, from the 
Margate flats in Kent; from Cornwall and other English shores, 
The specimen figured in the annexed Plate is from Scarborough in 
Yorkshire ; thofe found on the coast of Wales and Scotland, and 
particularly the Orkneys, are not inferior in point of size to those 
from scarborough. 
