358 MR. ALDER ON ADDITIONS TO THE MOLLUSCA 
subject to the same process ; and as the farmer repeatedly ploughs 
over and harrows the stubborn soil, so has nature, in the course 
of ages, ploughed over the earth’s surface by the action of the 
elements—by currents of water—by volcanic forces—by glacier 
and iceberg—breaking up the rocks and grinding and comming- 
ling the materials in order to form a surface-covering adapted to 
the wants of humanity. 
XV.—Additions to the Mollusca of Northumberland and Durham. 
By Josuua Axper, Esq. 
[Read Wednesday, December 12th, 1849.] 
Srnce the publication of our Catalogue of Mollusca in the spring 
of 1848, a few additional species have occurred of which I now 
propose to give an account. These have been principally got 
during three days’ dredging off Whitburn last summer, in which 
I had the assistance of Mr. Howse, who kindly went out with the 
fishermen on two occasions. My own share in the transaction 
was, for the most part, confined to an examination of the mass of 
submarine products dredged up, which was brought on shore in 
order that the treasures it contained might be selected out care- 
fully and at leisure. The result of these dredgings was very 
satisfactory. One hundred and seven species of Mollusca were 
obtained, including several rarities, amongst which were six species 
not before observed on our coast: one of them I consider new and 
undescribed. 
Besides the Mollusca, several crabs, star-fishes, and zoophytes were 
brought in, of which no account was preserved. The depth dredged 
in was between twenty and thirty fathoms, at a few miles’ distance 
from the shore, and the space did not extend beyond Marsden on 
