83 



of the lateral margin an angle of about 130; foramen about as wide as 

 high. Dorsal valve moderately convex, largely compressed at the cardinal 

 angles, a wide, shallow mesial sinus extending to the beak ; umbo incon- 

 spicuous; foramen wide, triangular, and without a divaricator process; area 

 almost linear, lying nearly in the plane of the lateral margin. Surface 

 with fine bifurcating ribs, 4 or 5 in the width of one line, with usually a 

 much finer one between each two of the larger. 



Width 5 lines ; length 3 lines. 



This species is much broader than 0. Electra, and has the dorsal valve 

 more convex. 



Locality and Formation. Point Le*vis ; in the upper part of limestone 

 No. 2, Quebec group. 



Collectors. Sir W. E. Logan, J. Richardson. 



. ORTHIS EUDOCIA. (N. sp.) 



Fig. 76. a, 6, c. 



Description. Semi-oval ; hinge-line equal to the greatest width of the 

 shell ; cardinal angles apparently rectangular ; sides vsomewhat straight, 

 and sub-parallel for two-thirds the length ; front angles and margin 

 uniformly rounded. Ventral valve' gently convex ; greatest height in the 

 upper half, sloping with a slightly convex descent to the sides and front 

 margin; beak nearly of the same height as the shell, very slightly 

 depressed ; area moderate, flat, extending to the cardinal angles, forming 

 with the plane of the lateral margins an obtuse angle of about 120; 

 foramen large, extending to the beak. Dorsal valve flat, with a slight 

 concavity in front of the beak, along the middle. Surface with fine striae 

 of unequal size, about 8 in the width of one line, at the front margin ; of 

 these, usually about three are much stronger than the others. 



Width 8 lines ; length of ventral valve 7 lines ; height of area at the 

 beak 1 lines. The dorsal valve is a little shorter than the ventral. 



Closely allied to 0. tricenaria, from which it differs only in having the 

 ventral valve less elevated, and the surface finely striated, instead of 

 coarsely ribbed. 



Locality and Formation. Point LeVis ; in the upper part of limestone 

 No. 2, Quebec group. 



Collectors. Sir W. E. Logan, J. Richardson. 



