The 'N:ew Species of Brachiopoda. 83 S 



original specimen, 8 mm., width, 6 mm., thickness through the 

 apices of the conjoined valve, 3 mm. 

 Trenton limestone. Middleville, iV. Y. 



Orbiculoidea numulus. 



Plate 2, fig. 11. 



Orbiculoidea numulus, Hall. Palaeontology of N. Y., vol. VIII. pt. 1, p. 178, 

 pi. ive, fig. U. 1892. 



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, JV. Y. 



Orbiculoidea Herzeri. 



Plate 2, figs. 14-20. 



Orbiculoidea Herzeri, Hall. Palaeontology of N. Y . , vol . VIII, pt. 1, p. 178, pi. 

 iv e, fig. 19, and pi. iv f , figs. 9-13, 30. 1892. 



Shell subcircular in outline. Upper valve with an eccentric 

 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 extend- 

 ing 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, Baconshurg and 

 elsewhere^ Ohio. 



