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PALEONTOLOGY OF NEW YORK. 
It is referred to the genus Gosselettia of Barrois, from the Devonian of 
Spain, on account of its similarity of external form and the strong cardinal 
teeth ; otherwise it has all the characters of Mytilarca. 
Formation and localities. In the shales of the Hamilton group, Fultonham, 
Schoharie county, and Onondaga county, N. Y. 
Gosselettia retusa. 
PLATE XXXIII, FIGS. 1, 2. 
Gosselettia retusa, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 30, figs. 1, 2. Jan., 1883. 
Shell of medium size; body very oblique, rhomboid-ovate, sub-arcuate ; length 
one-third greater than the height; ventral margin nearly straight for two- 
thirds of the length, inflated at the byssal opening and concave below, 
thence abruptly curving into the broad basal and dorsal margin. 
Valves equal, regularly convex in the posterior part and gibbous in the 
umbonal region; the point of greatest convexity is above the middle. 
The ventral umbonal slope is sub-angular. Ventral side flat. 
Hinge-line short. Beaks acute, prominent, directed a little forward and 
incurved. 
Test of moderate thickness, marked by lamellose concentric lines of 
growth which at irregular distances are crowded into fascicles. 
Ligamental area and interior unknown. 
The specimen described has a length of 49 mm., height 32 mm., breadth 
30 mm. 
This species differs from G. triquetra in its proportionally longer form, which 
is less expanded posteriorly ; hinge-line shorter and less oblique to the body of 
the shell; and the ventral umbonal slope is less angular along the length. 
Formation and locality. In the Hamilton group, Eighteen mile creek, Erie 
county, N. Y. 
