178 PALEONTOLOGY OF NEW YORK. 



Orbiculoidea numulus, sp. nov. 



PLATE IV 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 Ibramen is moderately broad and extends one-half the length of the 

 po.sterior 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 Hue concentric lines. Length and width, 12 mm. 



Lower Helderberg group (Waterlime). Marshall, N. Y. 



Orbiculoidea Herzeri, sp. nov. 



PLATE IV E, FIG. m; and PL.VTE I Vf, 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 l)ackward. 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 tiat. 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 

 gi-oove 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, Baconshirg and elsewhere, Ohio. 



Lindstbcemella aspidium, gen. et sp. nov. 



PLATE IV E, FIG.S. 25-28. 



This species is readily distinguished from Orbiculoidea {Ramerella) grandis, its 

 associate in the fauna ol' tlu; Hamilton shales, and the only form with which 



