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There were also exhibited Fossil Oysters from Croydon by Dr. 
Carpenter, Plants of Drosera Rotundifolia from Keston, by H. M. 
Klassen, and Nest of Tree Wasp by E. Lovett. 
October 20th 1875.—Alfred Carpenter, Esq., M.D., in the chair. The 
minutes of the last meeting having been read and confirmed, 
and the Chairman having alluded to the unavoidable absence of the 
President, who was in Paris, the following gentlemen were nomi- 
nated for election at the next meeting, viz.:—Messrs. Arthur 
Birkitt, J. B. Fawcett, John Jaques, and Michael Pope. 
At the request of the Chairman, Mr. J. 8. Jonnson, M.R.C.S., 
then read the following paper ‘‘ On tHe Anatomy oF THE Marine 
Musseu.”—The common mussel (Mytilus Edulis) belongs to the 
class Lamellibranchiata, and division Anodontophora, indicating that 
it is devoid of any tongue. It frequents mud banks which are un- 
covered at low water. The fry abound in water a few fathoms deep; 
they attain their full size in a year. The mussel is much used as 
food, but at times, from some unknown cause, it is extremely dele- 
terious ; they are largely used as bait in fishing for cod. The shell 
is wedge-shaped, equi-valve, but slightly inequilateral, pointed 
anteriorly, rounded behind, it is secreted by the thick edge of the 
mantle, the thin edge of which secretes the nacre, lining the interior. 
Hither between the mantle and the shell, or in the substance of the 
mantle itself, small pearls are frequently formed of an inferior 
quality (specimens were exhibited). Any foreign body of moderate 
size which is insoluble, and cannot be got rid of by the animal, is 
coated with nacre so as to isolate it. The outer surface of the shell 
is coated by a horny or chitinous membrane, called the periostracum, 
which is secreted by the thick margin of the mantle and organically 
connected with it. If rubbed off with emery powder, the shell is 
semi-transparent, and of a rich violet colour, Mya Arenaria, Trun- 
cata, and some others called Gapore, being the exceptions. The 
shell is a close one. As in most bivalves, it is coated on the inside 
with nacre, the iridescence of which is caused by light impinging on 
an undulating surface, called diffraction. On the outer surface are 
the lines of growth, that nearest the umbo being the youngest. 
Mr. Johnson having, by means of diagrams, shown the positions of 
the various organs, the courses of the nerves, and the attachment 
of the mussels, continued,—The foot is of a muscular mass, 
hollowed out for the lodgment of the digestive and reproductive 
organs. It is retracted by two pairs of muscles, which give firm 
points of support, resisting the strain frequently put on the byssus; 
the anterior pair diverge on either side from the edge and anterior 
part of the foot to the dorsal position of the side of the anterior 
adductor, and pass between the tentacles and by the side of the 
mouth, supporting the esophagus; the posterior are fan-shaped, and 
