LAMELLIBRANCHIATA. 329 



LED A, Schumacher. 1817. 

 Leda diversa. 



PLATE XLVII, FIGS. 31-37. 



Leda (Nuculana) diversa. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : Pi. 47, fi^. 31-37. 



1883. 



Shell small, ovate-cuneate ; length about twice the height ; basal margin curv- 

 ing in the anterior portion, becoming straight or nearly so, behind. Posterior 

 extremity acuminate. Cardinal line straight, oblique. Anterior end propor- 

 tionately large, declining rapidly from the beak and regularly rounded below. 



Valves gibbous in the anterior and umbonal regions, attenuated behind. 



Beaks at about the anterior third, prominent, incurved, rising above the 

 hinge-line. Umbo prominent, obtuse. Umbonal ridge sub-angular, extend- 

 ing from the beaks to the posterior extremity; the surface sloping abruptly 

 from this ridge to the hinge-line. 



Surface marked by fine, regular, concentric striae which are merged into 

 the umbonal ridge and are obsolete on the cardinal slope. Interior unknown. 



A specimen of the usual form has a length of 10 mm. and a height of 5 

 mm. A somewhat larger and shorter individual has a length of 11 mm. and 

 a height of 6 mm. 



This species differs from L. brevirostris in being narrower and more elongate 

 posteriorly, with more anterior beaks, and more direct umbonal ridge. 



Formalion and localities. In the soft calcareous shales of the Hamilton group, 

 at Bear's gulf and Jefferson, in Schoharie county, and in Onondaga county, 

 N. Y. 



Leda brevirostris. 



PLATE XLVII, FIGS. 38-41. 



Ledaf brevirostris. Hall. Pi-elira. Notice Lamellibranchiata, 2, p. 6. 1870. 



Leda (Nwulana) brevirostris. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 47, figs. 38, 39 



(40, 41 ? ). 1883. 



Shell small, ovate-triangular, abruptly nasute behind ; length about one-third 

 greater than the height; basal margin broadly curved in the anterior por- 



