290 
Aug. F. Foerste 
centric undulations of growth. Although the anterior margin 
of the shell is not preserved, enough of the shell anterior to the 
beak is seen to indicate that the concentric striae and obscure 
undulations are not gathered up anteriorly into a series of strong- 
concentric folds, as in Rhytimya, nor are there any obliquely radi- 
ating series of granules between the umbonal ridge and the basal 
•margin as in characteristic species of that genus, to which the 
present form evidently is not related. 
Cardinal and basal margins subparallel posterior to the beak, 
the height being 11.5 mm. at the beak and 13 mm. at the posterior 
end. The anterior end of the type specimen is defective but 
enough remains to indicate that it projected about 11 mm. an- 
terior to the beak. Length 38 mm., convexity of single valve 
about 4 mm. 
Locality. Type, associated in the same slab with numerous 
fragments of a Strophomena resembling Strophornena hecuha, one 
good specimen of Rafinesquina alternata, one of Pterinea dernissa, 
and apparently a fragment of Catazyga headi; collected on the 
beach below Becancour river, and therefore presumably along 
the St. Lawrence river, October 3, 1852, by James Richardson; 
forming specimen No. 2144, Palaeontological Collections, Geologi- 
cal Survey of Canada, Victoria Memorial Museum, Ottawa, 
Canada. 
In the subparallel outline of the shell and in the angularity of 
the umbonal ridge this species resembles Orthodesma, but there is 
no evidence of a conspicuous anterior muscular scar; however 
only the exterior of the shell is presented. The general aspect 
of the shell is somewhat like that of Cymatonota, but there is no 
indication of oblique undulations along the cardinal margin, and 
the umbonal ridge is more angular. Compared with Modiolopsis 
postplicata, both the cardinal and basal margins are straighter, 
the umbonal ridge is more angular, there is no trace of a mesial 
sulcus, nor of an anterior muscular area, and the prominent ob- 
lique striae along the hinge-line are more numerous. 
25. Cymatonota lenior, sp. nov. 
{Plate I, Fig. 9) 
Shell with the general aspect of a Cymatonota but without the 
oblique wrinkles along the hinge-line, posterior to the beak. The 
