SALTER — A CHRISTMAS LECTURE ON COAL. 
179 
The Hinge, vrlien the valves are opened — they are rarely so — does 
not present the usual teeth of Unio ; but the binding ligament of tho 
hinge has nearly the same position. Moreover, the Unio shell has — 
besides the scars left by the two great muscles which close the shell 
— a smaller scar (or even two) next to the front muscles ; and 
this is absent in the fossil. Professor King, of Galway, a close 
observer of the insides of " auld warld" shells, estabhshed this fact, and 
distinguished the fossil from Unio by means of it. He called the 
coal-shell Ardliracosia, a very appropiiate and even classical name. I 
heartily wish all palseontological names were so ! 
Fig. l.—Anihracosia (Unio) acuta, Sowerby. 
Fig. 3.— J. otalis, Martin, 
And I find, on carefully looking over a number of specimens, that 
every now and then one shows the whole surface of the shell wrinkled, 
not the beak merely^ but the broad surface of the shell itselt. This 
also is a character not found in the true Unio ; but is common to all 
the mud-burrowing tribes of the myadae or " gapers and to this 
tribe I would refer the shells in question. 
The more so, as another shell often accompanies the Aiithracosia, 
which clearly belongs to some family of mud-burrowing shells. It 
has the surface strongly wrinkled ; and 
these wrinkles are of such a shape as 
to indicate the existence of a rough 
strong envelope to the tubes of the 
mantle, like those of the Mya. Here is 
a sketch of the living Mya or " gaper," 
as it stands head downwards in its 
muddy home ; and side by side with it 
is the shell I have referred to, called 
by me Anthracomija. These really are 
the principal shells throughout the 
greater part of the coal-measures. And, 
so far as we know, all such shells must 
have Hved in salt-water, — though I am 
bound to say that an eminent man who 
has lately written on the shells of the 
coal of Germany, considers that some 
of them are like the freshwater muscle Breksena. I do not believe 
Fig. 4. — Mya tnnwafa, with its 
rough tiibe (Woodward). 
Fig. 5. — Anthracomya genex, \Tith 
its tube and foot restored. 
