DESCRIPTIONS OF SPECIES 369 



the pedicle, with the beak closely incurved beneath that of the pedicle 

 valve. In some specimens the cardinal slopes are less rounded, giving 

 the posterior portion of the shell a subtriangular aspect. 



The subcircular expression of the shell, its moderate and uniform 

 convexity, and the gently incurved beak distinguish this species. It 

 may most readily be compared with Whitfield's Nucleospira rotundata 

 from Greenfield, Ohio, but that species is usually represented by larger 

 specimens. 



A comparison with Whilfieldella nucleolata Hall of the Coralline lime- 

 stone of Schoharie shows considerable similarity between the two spe- 

 cies. The Coralline limestone species has, however, a more circular 

 expression, the width usually slightly exceeding the length. In other 

 respects the two species are very close. This species is not uncommon 

 in the friable bituminous portion of the Manlius limestone at Akron, in 

 the extreme eastern portion of Erie county, New York. It has so far 

 been found chiefly in the form of molds, both external and internal, the 

 shell being wholly dissolved. Characters of the exterior are often im- 

 pressed on the internal mold from pressure contact. Occasionally the 

 mold is filled with crystalline calcite, which forms a perfect cast of the 

 shell. 



An average pedicle valve measures 9 millimeters in length by 8 milli- 

 meters in width. The convexity of the valve is 2.5 millimeters. 



WHITFIELDELLA CF. LM VIS ( WHITFIELD) 

 (Plate 22, figures <±a-d) 



Compare Meristalla Imris Whitfield. Annals of the New York Academy of Sciences, 



1882, volume ii, page 195 ; ibidem, Geology of Ohio, volume vii, 1893, page 411, 



plate I, figures 6-7. 

 Compare Meristella Items (Vanuxem) Hall. Palaeontology of New York, volume 3, 



plate 39, figure 1. 

 Not Atrypa Isevis Vanuxem. Geological Report of the Third District of New York, 



1842, page 120, figure 2. 



Shell small, the largest specimen obtained not exceeding 10 milli- 

 meters in length. Pedicle valve broadly ovoid, gibbous, the greatest 

 gibbosity in the umbonal third. Longitudinal contour a symmetrical 

 curve, descending more abruptly in the umbonal region. Transverse 

 contour, a symmetrical arch flattened at the top, and with steep sides, 

 which approach verticality in the umbonal region. A faint depressed 

 line runs down the center from near the beak to the anterior margin. 

 Surface marked by fine concentric growth lines and by coarser wrinkles 

 appearing at intervals. 



