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Aug. F. Foerste 
flattened, with a moderate concavity toward the beak. The 
strong downward deflection anteriorly and laterally takes place 
from 10 to 11 mm. from the beak; and the anterior slope of the 
valve frequently reaches a length of 13 to 20 mm. In that case 
the shell has a triangular, or subpentagonal, nasute outline. The 
upper faces of the lobes of the cardinal process are flat, resting 
upon a callosity which extends laterally to the inner sides of the 
sharp crural plates, and anteriorly merges into the conspicuous 
median ridge separating the rather deeply impressed adductor 
scars. No conspicuous vascular ridges and sinuses were noticed 
anteriorly along the median parts of the shell, but distinctly 
defined grooves throughout the interior of this valve indicate 
the location, exteriorly, of the more prominent radiating striae. 
Deltidium of the pedicel valve less conspicuous than usual on 
account of the strongly developed chilidium of the brachial valve. 
The hinge-area is fairly high, the hinge-teeth are relatively 
coarse and strongly supported by the callosity filling in the space 
between the hinge-area and the general interior of the valve. 
In fact, both valves are thick, and represent gerontic condi- 
tions. The muscular area is subcircular, with the postero- 
lateral diductors narrow, bordering the support of the hinge-teeth. 
The area is crossed by a median ridge, as usual. The interior 
of the shell is thickened anteriorly, especially along the median 
parts, and there is a tendency toward a knotted’’ elevation of 
this part of the thickened border as in Strophomena nutans. The 
border is crossed by vascular grooves. 
The shell usually does not exceed 23 to 25 mm. in width. 
As far as the subpentagonal, nasute outline, and the strong 
median thickening of the interior of the pedicel valve are con- 
cerned, it is believed that these features do not suggest relation- 
ship to Strophomena nutans, but that they indicate similar geron- 
tic stages of two quite dissimilar species produced by a retarded 
growth of the shell, accompanied by an increased thickening of 
the valves, and a more sudden deflection of the anterior and 
lateral margins. Any marked increase in the amount of shell 
material added to the interior of the valves is likely to be accom- 
panied by a greater curvature of the valves, to provide the neces- 
sary room for the living parts, and if the lateral growth is greatly 
retarded, the additional room is provided anteriorly, resulting 
sometimes in a subnasute outline. 
