304 
Aug, F. Foerste 
at an angle of about 120 to 125 degrees. Surface marked by fine 
concentric lines^ not readily seen except under a lens. Cast of 
interior with a narrow, slightly sigmoid, clavicular adductor 
support impression just in front of the beak, forming an angle of 
65 degrees with the longitudinal axis of the shell, and extending 
about 2.5 mm, from the tip of the beak. Anterior to this clavic- 
ular support groove a shallow depression extends across the shell 
from the beak to the anterior part of the basal margin at an angle 
of about 55 degrees with the longitudinal axis. Anteriorly this 
shallow depression is bounded by a low transverse ridge or fold, 
also extending from the beak toward the anterior part of the basal 
margin, at an angle varying from about 45 degrees near the beak 
to 50 degrees near the basal margin. It is the shallow depression 
and low ridge or fold anterior to the clavicular support impression 
in the cast which are regarded as most typical of the form here 
described. 
Type. Richelieu River, near Chambly, collected by A. H. 
Foord in 1881. No. 2079, in Paleontological collections. Geolog- 
ical Survey of Canada, Victoria Memorial Museum, Ottawa, 
Canada. Associated with Glossograpius quadrimucronatus-approx- 
imatus, and Rafinesquina alternata. The type is represented by 
Fig. 12 on plate I. 
The two specimens represented by Fig, 6 on the same plate are 
regarded as belonging to the same species. They occur on the 
rear of the rock fragment containing the type of Psiloconcha 
sinuata-horealis. This fragment came from a group labelled as 
coming from the Riviere des Hurons, and as collected by Thomas 
Curry, in October, 1872, but no label is attached to the fragment 
itself. No, 8427. 
All of the figures are unsatisfactory, owing to the small size of 
the specimens. The engraver did not preserve well the outlines 
of the valves although these were clearly shown in the photo- 
graphic reproduction on the copper plate. Compared with 
CUdophorus planulatus^ the valves are relatively lower and longer, 
and the clavicular adductor support is more oblique, although the 
amount of this obliquity apparently is a variable feature. 
Specimens resembling CUdophorus praevolutus occur also half 
a mile south of the station at St, Hilaire, in a ditch along the road. 
