4 
PROCEEDINGS OE THE ACADEMY OF 
/■' 
* v 
r 
width at the two extremities. A similar undescribed species occurs in the 
“ fine-grained sandstone’’ of Ohio. 
DISCINA, Lamarck. 
Discina patellaris, n. sp.—Upper valve circular, elevated, patelliform, 
with a subcentral beak, from which the surface slopes in right lines to all 
parts of the margin, except a barely perceptible concavity down the posterior 
Slope. Surface (of cast) with feeble concentric striae. 
Diameter -90 (100); height of upper valve *33 (37); The length appears to 
be a very little greater than the breadth, but the specimen is slightly defective 
posteriorly. 
This species recalls D, Alleghania , Hall, of the Chemung Group, but the apex 
is more central, and the concentric lines less lamellar and regular, and the 
shell, so far as known, is smaller. 
PRODUCTA, Sowerby. 
Producta ? parvula, n. sp—Shell very small, semi-elliptic or nearly semi¬ 
circular in outline, with a hinge-line equalling the greatest width, or a little 
less. Yentral valve ventricose, with regular, though slightly diminishing 
curvature from beak to anterior margin, describing an arc of about 180°; 
beak elevated above the hinge-line and incurved over it; flanks regularly 
convex, abruptly flattened and auriculate at the hinge extremities. Dorsal 
valve unknown. Surface ornamented with small, rigid, continuous, radiating 
ribs, which on the sides increase by implantation. 
Length from beak to anterior margin -38 (100); width *31 (82); depth of 
ventral valve -23 (61). The prevailing dimensions are less than the above. 
Amongst Products of similar age the miniature size of the present species 
renders it at once distinguishable. The specimens look like pygmy examples of 
P. cor a , arcuala or pileiformis. 
Producta Martini, (Sow.) de Kon. (P. semireticulatus , Martin.)—In the wide 
range of characters admitted into this species, as defined by de Koninck, there 
is little doubt that the Burlington specimens would be embraced. Although 
most of the American species of Producta formerly identified with European 
types have subsequently been separated, P. Martini (or semireticulatus ) is still 
admitted to exist in our coal measures ; and it seems probable that its first ap¬ 
pearance dates considerably further back. 
Ranges from the bottom of the Yellow sandstones into the Burlington 
limestones. 
Producta speciosa, Hall, (Tenth Ann. Rep. Reg. N. Y., p. 176).—Several casts 
of this Chemung species present the appearance of being inside views of very 
concave dorsal valves ; but no internal structures are visible. The beak is 
flattened, and not elevated above the hinge-line, which is somewhat shorter 
than the greatest width of the shell. The other characters also agree. 
STROPHALOSIA, King. 
Strophalosia ? nummularis, n. sp.—Shell of medium size, circular, trunca¬ 
ted by the hinge-line. Hinge-line (generally much) shorter than the greatest 
width of the shell. Yentral valve comparatively very shallow, regularly arch¬ 
ing from the anterior side to the vicinity of the beak, which is obtuse, not in¬ 
curved and not elevated above the dorsal margin; surface depressed each side 
of the beak; area apparently present, but very narrow. Dorsal valve discoid, 
with a broad, shallow umbonal depression, which is bounded on the two sides 
by lines diverging from the beak at right angles with each other, or nearly so ; 
beak depressed, furnished with a small bifid cardinal process or boss, which 
lies in the plane of the valve and projects beyond the hinge-line ; each branch 
of the boss continued internally in a low vanishing ridge, which is turned out¬ 
wardly into the position of a socket ridge, but without the socket behind it; 
' j : , [\T3-Q. 
frlA* „ d-V. h . 
1 
