84 
middle of Hie shell, and in wanting the constriction and the 
subtmncated anterior end 
Martjn’s figures, tab 27 and 28, appear to be the same 
species as this; they were then understood to be the same 
species as My a ovata of Linn. Trans, which was not 
distinguished from Mya ovalis, but it differs from that in 
the outline, which is a regular uniform curve, without any 
angles at the end, as in recent shells. Those specimens 
that have angles, are evidently distorted ones, and most of 
them appear to have slipped from the hinge a little. This 
was found in marie at Felmersham in Bedfordshire, by my 
very kind old friend the Rev. T. O. Marsh. The specimens 
sometimes bear so much resemblance to the Derbyshire ones, 
that they are taken for the same even when found in the 
alluvial soil near Bedford. Tab. 99, British Mineralogy, 
exhibits the inside of a pyritaceous cast resembling it, from 
n Bath. 
UMIO acutus. 
TAB. XXXIII. —Figs. 5* 6, and 7. 
Spec. Char. Anterior side acute, twice as wide as 
the other which is blunt or rounded. Width 
two and an half times its length. 
Posterior side deeper than the anterior, beak rather 
angular, size the same as the two last. 
Plentiful among argillaceous Iron-stone in the neigh- 
bourhood of Bradford in Y orkshire. I am favoured with 
the shorter variety by Samuel Hailstone, Esq. The other 
was sent me by Mr. Jonathan Salt; I believe it is from 
Derbyshire. The lowest figure is taken from one which I 
suppose to be a cast of the inside. 
In order to prove the identity of these shells with the 
Genus Unio of Lamarck, which their external characters 
led us to suspect, we have made a cast of the inside of a 
recent species, upon a comparison of which with several 
fossil casts we are enabled to give it as our decided opinion, 
that these shells are undoubtedly of the same genus, conse- 
quently we have several species of fresh water shells in one 
of our Coal formations, and we have great reason to believe 
that the Mytillus crassus figured in Brit. Min. tab. 386, 
may also be considered as a fresh water shell, as it appears 
to be an Anodonta of Lamarck. 
