174 
PALAEONTOLOGY OF NEW YORK. 
Monomerella Greenii, sp. nov. 
PLATE IV D, FIGS. 5-10. 
Shell elongate-subovate. Valves comparatively shallow; shell-substance 
relatively thin. Surfaces of contact very broad, especially toward the 
posterior portion of the shell. Pedicle-valve with an erect but not high 
cardinal area, which is continuous with the broad margins. Umbonal cavi¬ 
ties very short, rarely reaching to the hinge-line and sometimes scarcely more 
developed than in Dinobolus. Cardinal slope well defined and divided by a 
deep longitudinal groove. Cardinal buttress faint. Platform scarcely devel¬ 
oped ; the scars upon its surface usually faint, but the lateral impressions are 
sometimes sharply defined. Crescent and terminal scars generally distinct. 
Pallial sinuses usually discernible. Brachial valve with a low, rotund beak 
and transversely striated area. Umbonal cavity deep. The deep groove of 
the crescent is followed within by a sharply elevated ridge extending for the 
entire length of the cardinal line ; terminal scars generally deeply impressed 
and apparently compound. Platform represented only by a median thicken¬ 
ing of the muscular impressions, having the characteristic V-shaped outline 
and sometimes divisible into the component scars. From the anterior ex¬ 
tremity of this muscular area two diverging ridges pass toward the anterior 
margin; these may be connected with the pallial sinuses. 
This shell is readily distinguished from all other described species by the 
general tendency toward suppression of the platforms and muscular scars, the 
broad surface of contact, and the diverging anterior furrows of the brachial valve. 
From the dolomites of the Niagara group, between Cedarburgh and Grafton, 
Wisconsin. 
Monomerella Kingi, sp. nov. 
PLATE IV D, FIGS. 1, 2. 
Shell subcircular or longitudinally oval. Pedicle-valve probably with a low 
cardinal area, as far as may be judged by the size of the casts of the umbonal 
cavities, which are quite short, mammiform, not extending to the cardinal 
line. Cardinal buttress strong, produced as a septum nearly to the anterior 
edge of the platform. Platform well developed, broadly V-shaped; anterior 
wall vertical, not excavated; surface marked by strong impressions of mus- 
