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PALAEONTOLOGY OF NEW YORK. 
Orbiculoidea numulus, sp. nov. 
PLATE XV E, FIG. 14. 
The original specimen is a lower valve, having a nearly circular outline. 
The apex is subcentral, elevated and directed anteriorly. The external groove 
of the foramen is moderately broad and extends one-half the length of the 
posterior radius. The posterior slope is convex while the anterior is depressed 
or slightly concave. Surface smooth about the apex, thence outward marked 
by a few distant, elevated, concentric lines or ridges, between which are 
numerous fine concentric lines. Length and width, 12 mm. 
Lower Helderberg group (Waterlime). Marshall , N. Y. 
Orbiculoidea Herzeri, sp. nov. 
PLATE IVE, FIG. 19; AND PLATE I VP, FIGS. 9-13, 30. 
Shell subcircular in outline. Upper valve with an excentric apex, situated 
less than one-fourth the length of the shell from the posterior margin, and 
directed backward. Surface gently convex, sloping evenly forward from the 
apex, but abruptly depressed on the post-apical region. Lower valve with 
the apex much nearer the center; shell almost flat. Pedicle-aperture, in the 
primary stages of development, a triangular opening extending from the apex 
to the margin; this gradually closes with advancing growth, the external 
groove at maturity extending from one-half to two-thirds the length of the 
posterior radius of the valve. On the interior, the groove is frequently more 
or less enveloped by the development of testaceous deposits. Surface of both 
valves ornamented by crowded concentric lines and wrinkles. The internal 
surface of the lower valve sometimes shows fine radiating lines and faint 
vascular sinuses. Length and width of an adult individual, 14 mm. 
Waverly group (Cuyahoga shales). Berea, Baconsburg and elsewhere , Ohio. 
Lindstrcemella aspidium, gen. et sp. nov. 
PLATE IV E, FIGS. 25-28. 
This species is readily distinguished from Orbiculoidea ( Roemerella ) grandis, its 
associate in the fauna of the Hamilton shales, and the only form with which 
