52 



the dorsal margin, to the lower posterior angle. The beaks appear to be 

 small and closely incurved. 



Surface covered with concentric ridges from one half a line to two lines 

 wide each. On the umbones, and on the anterior half of the shell, these 

 are rounded, but towards the posterior extremity, they become flattened 

 and sub-lamellose at their lower edges. 



Length of the largest specimen collected, thirty-three lines ; height^ 

 nineteen lines ; depth of a single valve, six lines. 



Locality and Formation — Gaspe ; lower part of the Gaspe sandstone. 



Collectors.- Sir W. E. Logan, R. Bell. 



MODIOMORPHA INORNATA. (N. sp.) 

 Plate 4, f.g: 4. 



Description, — Transversely sub-elliptical ; length, a little less than twice 

 the height. Dorsal margin, from the umbones to about one-fourth the 

 length from the posterior extremity, nearly straight, very slightly convex. 

 Ventral margin gently convex. Posterior extremity obliquely and ob- 

 scurely truncated, with a gently convex slope, in the upper half, uni- 

 formly rounded below,. most projecting point at about one- third the height. 

 Anterior extremity most prominent about the mid-height, rounded in the 

 lower half ; in the upper, apparently, obUquely truncated, with a gently 

 convex or nearly straight outline. The umbones are obscurely developed, 

 obtuse, about one sixth the length from the anterior extremity. Surface 

 with concentric striae, the stronger of which are one or two lines distant from 

 each other ; the finer ones apparently four or five in the width of one fine. 



Length, thirty-four lines ; height, nineteen lines ; depth of a single 

 valve, about six lines. 



The specimen -is a cast in sandstone, and apparently slightly flattened 

 by pressure. 



Localittj and Formation. — York River, Gaspe ; Devonian. 

 Collector.— Bell. 



Mytilarca Canadensis. (N. sp.) 



PI. 4, fig. 2, 2a. 



Description, — Outline of a cast of the interior, on a side view, semi, 

 ovate ; the anterior margin concave, for a short distance below the beaks, 

 and then nearly straight to the lower anterior angle, which is obtusely 

 rounded ; dorsal margin (in upper part) forming an angle of about 60^ 

 with the anterior, descending from the beaks with a nearly straight slope 



