50 



A. SUPERBA, n. sp. — Shell large, strongly ventricose, sub-cordiform. 

 Anterior and posterior sides gently convex and sub-parallel. Ventral 

 margin uniformly rounded. Hinge line equal to the whole length of the 

 shell, nearly ; posterior wing moderately prominent ; angle formed by the 

 hinge line and the posterior side about 100*^ ; anterior wing rudimentary. 

 The beaks, as shown in the cast, are scarcely incurved. There is a well- 

 developed area, between them, which extends the whole length of the 

 hinge line. Height from the middle of the ventral margin to the beaks, 3 

 inches ; length 2| inches ; depth of both valves about 2 inches. Junction 

 Cliff; Div. 1, A. G. T. C. Weston. 



A. RADiATA, Hall. — Occurs abundantly at Gamache Bay ; Div. 1, 

 A. G. Also in the H. R. 



A NiTiDA, n. sp. — Shell elongate, ovate, rather strongly convex ; beaks 

 small, terminal, closely incurved. On the anterior side the outline for a 

 short distance from the beaks is nearly straight, slightly concave, then 

 gradually rounded to the somewhat pointed ventral extremity. Beneath 

 the beaks there is an obscure lunette with a minute rudiment of an anterior 

 wing. Hinge-line short, straight, forming an angle of about 45° with the 

 longitudinal axis of the shell ; a very narrow area. Posterior margin 

 shghtly compressed, gradually and somewhat irregularly curved to the 

 ventral angle. The greatest convexity of the shell lies along a straight 

 line from the beak to the ventral angle. Surface with obscure concentric 

 strise which are impressed on the cast of the interior. Length 15 lines ; 

 width 9 lines ; depth of both valves 8 lines. One-fourth of a mile east of 

 Jupiter Biver ; Div. 3, A. G. 



Fig. 17. 



Fio-. IT. — Ambonychia nitida. a, anterior view ; 5, right valve. 



Genus Pterinea, Goldfuss. 



P. VARISTRIATA, n. sp, — Obhquely semi-elliptical or sub-rhomboidal 

 hinge line long and straight forming an angle of about 45<^ with the body 

 of the shell ; anterior wing short, rounded with a faint sinus at about one- 



