12 THE MOLLUSCA OF THE FIRTH OF CLYDE. 
British distribution.—Everywhere throughout our seas, 
from the shore down to 30 fathoms (forbes). 
Foreign localities.—Greenland (Fabricius), Iceland, var. 
semilaevis (Verkriizen), Maine (Binney, and others), Labra- 
dor (Whiteaves), Spitzbergen (Haton), Norway (Lovén). I 
have not found it recorded in M‘Andrew’s list from Spain, 
but Mr. Jeffreys includes the Aigean in its range. 
FAMILY ARCADE, Lowe. 
Nucuta, Lamarck. 
Nucula sulcata, Bronn. 
Nucula decussata, Sowerby. 
Habitat.—Scarce in Rothesay Bay in 20 fathoms, on a 
muddy bottom; only two or three specimens obtained. Mr. 
Barlee is said to have taken it at Tarbert, Loch Fyne; and 
Mr. Robertson has dredged it off Kilchattan Bay, Bute. It 
is evidently rare in our firth. 
British distribution —Sparingly distributed. The follow- 
ing localities are on record :—Oban and Raasay, in Scotland ; 
Dublin and Bantry Bays, in Ireland. 
Foreign locatlities—Norway (Lovén, Jeffreys, and others), 
Spain and Portugal (M‘ Andrew), Mediterranean and Aigean 
Seas and Sea of Marmora (Forbes, Spratt, and others). 
* Nucula nucleus, Linné. 
Arca nucleus, Linné ; Arca margaritacea, Bruguiére ; Nucula 
margaritacea, Lamarck. 
Habitat—In gravelly sand with an admixture of mud, 
from 8 fathoms downwards; very common throughout the 
district. The variety radiata is also obtained on the eastern 
side of Bute, and outside the Tan Spit, Cumbrae; but it is 
apparently scarce. 
British distribution.—Both the type and variety radiata 
are common throughout our seas at all depths, from a few 
fathoms downward. 
Foreign localities—Very widely distributed from Faroe 
Islands and Norway (Torell, and others) to Spain, Portugal, 
and Mogador (M‘Andrew), and throughout the Mediterranean 
and Avean (Forbes, and others). 
* Nucula nitida, G. B. Sowerby. 
Arca nucleus (probably), Montagu. 
Habitat—In sandy and muddy gravel, from 8 to 30 
