CARBONICOLA OBTUSA. 61 
margin, and suggested that the Unio tellinarius of Goldfuss and de Koninck, which 
is also stated to possess this character, may belong to Sowerby’s species. 
The only specimen showing the hinge-character of this species is in the Wood- 
wardian, and I have been allowed to figure it and other specimens from that collection 
by the kindness of Professor McKenny Hughes (PI. VI, fig. 44). In the drawing 
the fragment is looked at from below, and shows the lower edge of the hinge-plate, 
which is non-articular, the upper part of the plate being in consequence fore- 
shortened. 
This fragment shows a total absence of any prominence which can be con- 
structed into an anterior lateral tooth ; but there is a sloping surface continuous 
above the striated lunule, which becomes thickened and raised, immediately 
below the umbo, into an oblique posteriorly diverging cardinal tooth. Immediately 
posterior to it is a pit, so that the tooth in the right valve is immediately in front 
of that in the left valve ; the pit in the right valve has a plain triangular surface, 
and there is no evidence of any posterior lateral tooth. 
M‘Coy states (p. 515, op. supra cit.), ‘* Casts show the thick cardinal tooth, and 
slender, elongate, lamellar lateral teeth.” I am unable to understand this state- 
ment, as I cannot conceive it possible for the cast of a bivalve shell, the valves 
being in their natural position, to show anything of the sort. The Professor 
evidently mistook the groove left in casts on each side of the middle line by the 
lower edge of the hinge-plate, both anteriorly and posteriorly, to represent ante- 
rior and posterior lateral teeth. I have made a series of plaster casts of Unio 
tumidus, which have definite lateral lamellar teeth, but can obtain no indication 
of them in the casts. 
This shell does not appear to have a very wide distribution. I only know of 
the above-mentioned localities where it occurs; and it appears to be confined to 
the horizon of the Low Moor Ironstone beds. 
The large specimens, figured Pl. VII, figs. 11 and 15, belonging to Mr. George 
Wild, of Bardsley, are from the Fullege Colliery, Burnley, and at about the horizon 
of the Thin bed. 
7. CARBONICOLA OBTUSA, Sp. nov. Plate VII, figs. 16—23; Plate XI, figs. 1, 2. 
Specific Characters.—Shape variable, but more or less subquadrate and flattened. 
The anterior end is moderately convex, short but deep in a dorso-ventral direction ; 
its border circularly rounded. The inferior border is rounded in front, 
becoming almost straight posteriorly. The posterior part of the shell is narrowed 
from above downwards by the slope of the upper border, which leaves a long, 
bluntly rounded or truncate posterior border. 
