454 Prof. T. R. Jones and Dr. Woodward—A New Bivalve. 
sandstone, from the ‘#Carboniferous Shales” (or Lower Limestone 
of the Carboniferous-Limestone series), of Berwick-upon-T'weed. 
In the “Catalogue of the Collection of Fossils in the M.P.G.,” 1865, 
p. 116, it is referred to as “ Dithyrocaris pholadiformis” ; but whether 
or no this specific name was an alteration made by. Mr. Salter 
himself is doubtful. 
The specimen consists of two counterparts, one on each moiety of 
the split slab, showing impressions of the outside of one, and of a 
part of the inside of the other valve. 
“Seven inches” was evidently not the whole length of this 
extraordinary bivalved specimen, for probably more than an inch 
has been broken off at one end. Its width (height) is not wholly 
seen, for one valve (lying uppermost), broken away from the other, 
is shifted upwards to some extent over the perhaps more perfect 
dorsal edge of the other valve, and thus has lost probably a quarter 
or half an inch in that dimension. See woodcut, Fig. 1; half 
Fic. 1. Salterella pholadiformis, Lower Limestone Shales, Carboniferous Series, 
Berwick-on-T weed. 
natural size. As it lies in the stone, it has a boat-shaped outline, 
with an almost symmetrically elliptical curve on the lower border. 
The back, or upper edge, may have been either straight, or slightly 
convex, in its middle two-fourths; but it sloped downwards at a 
low angle towards the extremities on each of its terminal fourths. 
Hence, both in front and behind, at the junction of the two dorsal 
edges, there would be a slope, if the fossil were of a real bivalved 
form ; or a narrow slit, if the valves lay open, or if it were originally 
buckler-shaped, but since folded up. Numerous concentric lines of 
growth run parallel with the free edges; they are irregular in their 
thicknesses, and are thrown into undulations by about twelve 
transverse, radiating furrows and ridges of the valves. These 
flexures are more strongly pronounced on that moiety of the valve 
which happens to be more perfect than the other. 
The underlying valve or lateral moiety shows the lower part of 
the inner surface, below the outer or lower edge of the valve that 
lies uppermost. It shows longitudinal, concentric lines and trans- 
verse undulations, similar to those on the other (overlying) valve. 
Some matrix lies between the valves, as shown by a narrow seam of 
broken sandstone. 
