THE DEVONIAN FOSSILS OF CANADA WEST. 343 
Affinities and varieties.—This species stands nearer to 8. inequis- 
tirata than to any other. It differs from that species in the absence 
of a foramen, in the area being striated the whole length, in being 
more uniformly convex, and in the characters of the surface. There 
is little variation in the aspect, although the general contour differs 
somewhat. The ventral area varies from half a line to two lines wide, 
being almost linear in some specimens, and in others so wide as to 
give a low triangular form. In general the specimens from the 
corniferous limestone are smaller than those of the Hamilton group. 
I have seen none from the former rock more than one inch and a 
quarter wide; but many from the last mentioned formation with a 
breadth of one inch and a half. 
Locality and Formation.—In most of the localities of the cornifer- 
ous Limestone in Canada West. As yet, we have found none in the 
Hamilton group in Canada. My comparisons have been made alto- 
gether with specimens from the Hamilton shales of New York. 
Collectors.—E. De Cew, J. De Cew, E. Billings. 
STROPHOMENA PERPLANA.—(Conrad). 
STrROPHOMENA PERPLANA and 8. pLuRisTRIATA.—(Conrad). Jour- 
nal of the Academy of Natural Sciences of Philadelphia. Vol. 8., 
p. 257-259. Pl. 14, fig. 11. 
S. cRENRIsTRIA and 8S. rraqinis.-—(Hall). Tenth Annual Report of 
the Regents of the University of the State of New York. P.111-143. 
Description.—Nearly flat ; covered with fine, equal radiating striz. 
Width on hinge line from one to two inches ; length varying from a 
little more to one-fourth less than the width. In form, the shell is 
usually semioval—the front regularly rounded ; sometimes the sides 
are suddenly constricted just beneath the cardinal angles; often the 
sides are nearly straight and parallel for half the length, then uni- 
formly rounded to the fronts ; some have the front rather straight, 
giving a subquadrate aspect. The ventral valve is slightly convex, 
most elevated at about one-fourth or one-third from the beak, flattened 
towards the hinge line, often with a few obscure irregular concentric 
wrinkles. Dorsal valve gently concave. Area of ventral valve about 
one line wide at the beak, slightly concave. Area of dorsal valve 
about half the width of the ventral—the two areas inclined towards 
each other at an angle of about 90°. Both areas striated. No foramen. 
Surface covered with fine equal striz; from six to nine in the 
