SALTER — A CHRISTMAS LECTURE ON COAL. 



179 



The lunge, when the valves are opened — they are rarely so — does 

 not present the nsnal teeth of Unio ; but the binding ligament of the 

 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, established this fact, and 

 distinguished the fossil from Unio by means of it. He called the 

 coal-shell Anthracosia, a very appropriate and even classical name. I 

 heartily wish all palceontological names were so ! 



Fig. 2. — Anthracosia (Unio) acuta, Sowerby. 



Fig. 3.-^1. ovalis, 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 4 but the broad surface of the shell itsell. This 

 also is a character not found in the true Unio ; but is common to all 

 the mud-burrowing tribes of the myadee or " gapers ;" and to this 

 tribe I would refer the shells in question. 



The more so, as another shell often accompanies the Anthracosia, 

 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 My a. 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 Anthracomya. 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 lived 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 Dreissena. I do not believe 



Fig. 4. — Mya truncata, with its 

 rough tube (Woodward) . 



Fig. 5. — Anthracomya senex, with 

 its tube and foot restored. 



