346 THE DEVONIAN FOSSILS OF CANADA WEST. 
Fig. 119. 
Fig. 119 —STROPHOMENA AMPLA.—Halj. Dorsal Valve. 
also in the amount of its inclination to the plane of the lateral 
margin from 90° to 120° ; obliquely striated for one-third or one-half 
the distance between the foramen and the cardinal angles. Area of 
dorsal valve smaller than the ventral, of nearly a uniform width 
throughout, usually about half a line wide. Foramen small, linear 
closed, one-third of a‘ line in width. From the point where the 
Striation is discontinued the edge of the area of the ventral valve has 
a distinct narrow groove extending to the cardinal angle. 
Surface with moderately fine, somewhat equal, sharp, irregular strize, 
which bifurcate several times before reaching the margin; the number 
also increasing by interstitial addition; crossed by small concentric 
strie, which are usually more distinct in the spaces between the ra- 
diating strie. The radiating ridges are sometimes of a uniform size 
all over the shell, six to eight in the width of two lines; in others 
larger near the beak than towards the margin, diminishing in size from 
three or four in two lines at the beak, to six or eight in the same 
width at the margin. The surface characters are very variable within 
a small limit, but the general aspect is that of a sharp or angular 
somewhat rugose striation. When the shell is partially exfoliated, it 
is seen to be perforated along the bottom of the grooves between the 
radiating ridges by small circular or oval pores, of which there are 
from two to seven in the length of one line. These are indicated on 
