488 BRITISH PALALOZOIC FOSSILS. [ LAMELLIBRANCHIATA, 
The anterior ear of the right valve is narrow, truncate at the end, and with a very large notch between 
it and the body of the shell; posterior ear large, defined, falcate, and marked with strong lines parallel with 
the concave end. Both sets of strize are closer than in de Koninck’s figure. 
Position and Locality.—Rare in the carboniferous limestone of Derbyshire. 
AVICULOPECTEN PAPYRACEUS (Sow. Sp.) 
Ref. and Syn. = Pecten id. Sow. Min. Con. t. 354. 
Dese—Semiovate, truncated by the hinge-line, slightly oblique ; beak small, slightly convex, posterior ear 
large, slightly pointed, scarcely extending beyond the posterior edge of the shell, from which it is not defined 
by any notch in the margin, which is nearly straight at the junction, becoming slightly concave towards the 
point of the ear, and gradually convex towards the ventral margin; anterior ear in the left valve obtusely 
rounded, marked from the body of the shell by a shallow sinus in the margin; in the right valve it is smaller, 
and separated from the body of the shell by a deep narrow notch extending nearly to the beak; surface 
entirely covered with coarse, flattened, irregularly unequal, prominent ridges, separated by flattened spaces, 
usually rather less than the width of the ridges; the ridges increase in number but not much in size towards 
the margin, both by occasional branching and interpolation, all crossed by fine concentric striae scarcely visible 
to the naked eye except on the ears, where they become strong and regular, and about as far apart as the 
ridges. From beak to posterior ventral margin about two inches, proportional width at right angles thereto 7, 
length of posterior ear =, of anterior ear 5. 
From all the specimens being pressed quite flat, I have been unable to note the proportional depth, 
and perhaps it is from the same reason that there is no visible line of demarcation between the body of 
the shell and the ears. Our specimens are from the same locality as Sowerby’s original ones, so there can 
be no doubt of the identity. The anterior ear in Sowerby’s figure is made too pointed, and there should 
not be a marked definition of the margin between the body and the posterior ear: his upper and lower figures 
also only represent the two sides of one valve—the right valve haying a very different anterior ear. 
Position and Locality—V ery abundant in the coal shale near Bradford, but not in the same beds with the 
so-called Unio’s (Carbonicola), 
AVICULOPECTEN PERA (M‘Coy). 
Ref. and Syn. = Pecten pera M°Coy, Syn. Carb. Foss. t. 15. f. 19. 
Desc.—Ovate, moderately convex, front broad, apical angle 105°; ears very strongly defined from the 
body of the shell on each side, flattened, small, nearly equal; anterior one nearly rectangular, slightly acute ; 
posterior larger, but not extending more than two-thirds as far as the margin of the shell, pointed, its 
posterior end deeply sinuate near the middle; surface radiated with very numerous, close, fine, rugged, 
thread-like strive, alternately larger and smaller on most parts of the shell, separated by slightly wider flat 
spaces, crossed near the margin by sharp, concentric lines; about twelve longitudinal striz in the space of 
two lines at six lines from the beak: ears with about ten or twelve sharp, radiating strie, similar to those 
of the body, and crossed by very delicate strize. Length one inch three lines, proportional width from beak 
to ventral margin 7, length of posterior ear *, length of anterior ear 3. 
From the width, and slight convexity of the ventral margin, the outline resembles a bag or satchel, 
whence the name. I am not sure whether the radiating strie are spinose; in some lights they seem to be 
so, but the character is doubtful ; many specimens have the strize more nearly equal than subalternate. 
From the greater perfection of the English specimens I have no doubt a portion of the ventral margin must 
have been absent in the specimens I originally figured, making the ears appear too large; the perfect out- 
line more resembling that of the P. micropterus (M°Coy), Synop. W&e. t. 15. f. 12. 
Position and Locality—Not uncommon in the black beds overlying the limestone of Derbyshire. The 
original Irish locality was Townplots, Killala. 
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