THE DEVONIAN FOSSILS OF CANADA WEST. 269 
Width of largest specimen examined, eighteen lines; length, six- 
teen lines; thickness or depth of both valves, seven lines; height of 
area of ventral valve at the beak, one line; area of dorsal valve, four- 
fifths of a line ; distance between the beaks, one line ; length of hinge- 
line, ten Imes. The most common size appears to be one inch in 
width. The beak of the ventral valve is incurved, so that it would 
touch a plane projected horizontally through the valve, at one-half 
the depth of the cavity. 
In some specimens the ventral valve has a faint, barely perceptible 
mesial fold, extending from the umbo towards the front. 
This species is allied to O. Vanuxemi, but is more coarsely cattle 
It may be identical with one of the other species described in the 
Report of the Regents of the New York University, but as it is im- 
possible to identify it with any of the descriptions, I propose to name 
it as above. 
Locality and formation.—Township of Walpole. Corniferous 
Limestone. 
Collector.—J. De Cew. 
Ortuis VanuxEemMi.—(Hall.) 
Fig. 17. : Fig. 18. 
Fig. 17. Orthis Vanuxemi.—Ventral valve. Fig. 18.—Longitudinal section of the same. 
Fig. 19.—Dorsal aspect. 
Ortuis Vanuxemi.—Hall. Tenth Annual Report of the Regents of 
the University of the State of New York, p. 135, 1857. 
This species is closely allied to O. Livia, but is more nearly a perfect 
ellipse, or more nearly circular, and has about fifteen radiating striee in 
the width of three lines. Its width is from nine to eighteen lines, and 
its length about one-sixth or one-seventh less than its width. 
It occurs in the Hamilton Shales, in the Township of Bosanquet. 
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