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the ridges in width. In very perfect specimens, very fine concentric 

 sub-lamellar concentric strise are visible, seven or eight to one line. In 

 certain conditions of preservation alsO; the radiating ridges are seen to be 

 sub-tubular, and exhibit numerous small oval or circular openings on their 

 edges, each about the eighth or tenth of a line in width, and from one- 

 fourth to two-thirds of a line distant from each other. 



Width of largest specimen examined, eighteen lines ; length, sixteen 

 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 lines. 

 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 horizon- 

 tally 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 (9. Vanuxemi^ but is more coarsely striated. 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 impossible to identify 

 it with any of the descriptions, I propose to name it as above. 



Locality and Formation. — Indian Cove, Gasp^ ; No. 8. It occurs 

 also in the Corniferous limestone in Ontario and New York. 



Collectors. — Sir W. E. Logan, R. Bell and T. C Weston. 



Orthis Aurelia. (N. sp.) 



Plate 3, fig. 3. 



Description. — Of this species only two specimens have been collected, 

 one of the ventral and the other of the dorsal valve ; both imperfect. It 

 appears to be semi-elliptical, width fifteen lines ; length about twelve lines. 

 Ventral valve rather strongly convex, most elevated at three lines from 

 the beak ; thence sloping gradually with a gently convex curve to the 

 front, and concave on each side of the umbo outwards towards the cardi- 

 nal angles. The umbo at three lines from the beak is elevated, four or 

 five lines above the plane of the lateral margin ; beak incurved. Although 

 buried in the stone, judging from the height of the umbo, it would appear 

 that this valve has a large triangular area, probably extending out to the 

 angles. The dorsal valve is also convex, most prominent at about one- 

 third the length from the beak, which is considerably depressed below the 

 most elevated point of the !. 11. 



Surface with about twenty-five strong rounded ribs, each about one- 

 third of a line in thickness and somewhat less in height, distant from each 



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