Lorraine Faunas of New York and Quebec 275 
It occurs also at lower horizons than those exposed at Pulaski; 
for instance in the Lorraine Gulf, where it was cited by Emmons 
from within 4 feet of the upper part of the Triarthrus zone. 
Along the Nicolet River, in the province of Quebec, Byssonychia 
radiata ranges through the Proetus zone and downward into the 
upper part of the Trinucleus zone. Upward, it appears to range 
as far as the upper parts of the fossiliferous Richmond, just be- 
neath the Queenstown shale, but this requires confirmation since 
the Nicolet River section was studied before numerous typical 
specimens from the Lorraine of New York were at hand. 
14. Colpomya faba-pusilla, var. nov. 
{Plate II, Fig. 10; Plate III, Fig. 4 A, B) 
Greatest length of largest specimens known about 10 mm., 
cardinal margin straight for a distance of about 5 mm. posterior to 
the beak, rounding into the oblique posterior margin of the shell. 
There is considerable variation in the obliquity of this posterior 
margin ; in the shells having a more vertical posterior margin, the 
length of the straight hinge-line posterior to the beak may equal 
nearly 6 mm., while in the shells having a strongly oblique pos- 
terior margin the straight hinge-line may extend but slightly more 
than 4 mm. beyond the beak. Mesial sulcus strongly defined 
from the beak to the basal margin, its deepest part forming an 
angle of about 70 degrees, varying in some shells to 60 degrees, 
with the cardinal outline. Anterior to the mesial sulcus the shell 
is only moderately convex. Posterior to this sulcus, however, 
along the umbonal ridge, the shell is strongly convex, this con- 
vexity becoming almost angular toward the beak. The angle 
between the umbonal ridge and the cardinal margin varies usually 
between 40 and 45 degrees. Anterior margin more narrowly 
rounded, extending about 2 mm. anterior to the beak. 
Maximum length, measured diagonally, 10 mm.; height pos- 
teriorly, between 5.5 and 6 mm. ; height at the beak, about 4.5 mm., 
but varying from a little less to a little more than this height; 
convexity of the single valve, about 1.75 mm. in shells showing the 
strongest convexity. 
Surface with very fine concentric striae, visible under a lens. 
Interior with a small muscular scar near the upper anterior margin; 
