338 
MOLLUSCA. 
the following year, the mussels on it were not more than ^ an inch in 
length. 
Sept. 1, 1843. The light-ship was moored at Holy wood Bank, and on 
being brought into dock, on Nov. 15, 1844, to have her bottom cleaned, it 
was covered with full-grown mussels, which were carried away by persons 
to eat. If we knew the size these were when they moored themselves to 
the ship, the problem is solved of how long they are attaining full size. 
July , 1845. Mr. Hyndman showed me mussels nearly 1^ inch long, of 
which quantities were taken from the bottom of the pilot-boat after its 
being nine months afloat. 
Genus Crenella. 
C. decussata , Laskey. 
A few odd valves dredged in rather deep water — shelly bottom — in 
Strangford Lough, Aug., 1837, Mr. Hyndman and W. T. 
Genus Modiola. 
M. vulgaris, Br. 
Common on the North and North-East coasts in rather deep water on 
muddy and shelly ground ; used as bait by fishermen in some places, but 
not commonly as human food ; called horse-mussel. Apparently scarce or 
wanting in such of the bays of Mayo and Galway as w 7 ere dredged by 
our party in 1840. M. Gihbsii took its place in some localities. 
Modiola vulgaris. According to my journal, note of Dec. 14th, 1837, 
I find that full-grown individuals lived without water four days in a 
warm room, and that smaller individuals lived under similar circum- 
stances eight days. 
M. tulipa, Lam. 
Very rare. Belfast Bay, Mr. Hyndman and W. T. Malahide, Dublin 
coast, one or two specimens, Dr. Lloyd. Portmarnock, very rare, Mr. 
Warren. Birterbuy Bay, Dr. Farran. In or near Bantry Bay, Mr. 
M ‘Andrew. 
M. Gihbsii, Leach. 
Dredged in Clew and Killery Bays by our party in 1840, 3 — 12 
fathoms. M. Gibbsii is noted in Mr. Barlee’s list of Birterbuy Bay 
species, with a query as to its being a variety of M. vulgaris. Youghal, 
very rare, Dr. II. Ball. 
M. discrepans, Mont. 
“ Found on oysters in Dublin Bay,” (O’Kelly) ; I have seen specimens 
from thence in Mr. Warren’s collection. Larne Lough, not uncommon. 
Donaghadee, 8 to 10 fathoms, Dr. Drummond. Wicklow and Wexford 
coasts ; Youghal, Dr. It. Ball. Cork harbour, Mr. Humphreys. Dredged 
in Killery and Clew Bays, in 1840. Birterbuy Bay, Dr. Farran. This is 
a much less common species than the following. 
M. marmorata, Forbes. 
Dublin coast and Strangford Lough, BroAvn. Common on the North 
and North-East coasts, more especially embedded in various species of 
Ascidia : found loose also, sheltering among Balani and other excre- 
scences on oysters, &c. 
