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 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 line concentric lines. Length and width, 12 mm. 



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



Orbicdloidea Herzeri, sp. nov. 



IM.ATE IVE, FIG. 19; AND PLATE I V F, 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 evenl}' forward from the 

 apex, but abruptly depressed on the post-apical region. Lower valve with 

 the apex much nearer the center; shell almost Hat. 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. Surfjice of both 

 valves ornamented by crowded concentric lines and wrinkles. The internal 

 surface of the lower valve sometimes show.s fine radiating lines and faint 

 vascular sinuses. Lensrth and width of an adult indiviilual, 14 mm. 



n 



Waverly group (Cuyahoga shales). Berea, Buconsburg and elsewhere, Ohio. 



LiNDSTRCEMELLA ASPIDIUM, geil. et sp. UOV. 

 PLATE IV E, FIGS. 25-28. 



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

 associate in the ftxuna of the Hamilton shales, and the only form with which 



