. The Canadian journal of industry, science and art. 346 THE DEVONIAN FOSSILS OF CANADA Fig. 119. Fia;. 119 —SteophomenA ampla.—Hall. Dorsal Yalve. 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 o
. The Canadian journal of industry, science and art. 346 THE DEVONIAN FOSSILS OF CANADA Fig. 119. Fia;. 119 —SteophomenA ampla.—Hall. Dorsal Yalve. 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 & distinct narrow groove extending to the cardinal angle. Surface with moderately fine, somewhat equal, sharp, irregular striae, which bifurcate several times before reaching the margin ; the number also increasing by interstitial addition; crossed by small concentric striae, which are usually more distinct in the spaces between the ra- diating striae. 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 OA^al pores, of which there are from two to seven in the length of one line. These are indicated on. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Canadian Institute. Toronto : Canadian Institute
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