14 



tion to the height. Macasty Bay, and near the West-end Light-house 

 H. R. J. Richardson. 



Fig. 2. 



Fig 2. — Qyrtodonta? pleheia. — Three views of a specimen destitute of 

 the shell. 



C ? PLEBEIA, n. sp. — Obliquely ovate or obscurely rhomboidal, strongly 

 ventricose. In the cast of the interior the beaks project beyond the 

 anterior extremity, which is rounded and not strongly developed. The 

 ventral margin is moderately convex the whole length ; dorsal margin 

 sloping from a httle in front of the mid-length to the pointed posterior 

 extremity. Beaks small, incurved, but not in contact. On a dorsal view 

 the outhne is cordiform, the umbones angular on the upper side. Length 

 12 lines ; height about 6 hnes ; depth of both valves 8 lines. Charleton 

 Point ; H. R. J. Richardson. 



C ? Anticostiensis, n. sp. — Shell rather strongly convex ; anterior 

 extremity short rounded ; ventral margin straight or slightly convex for a 

 short space partly in front of the mid-length ; posterior extremity broadly 

 and nearly uniformly rounded, the most projecting point a little below the 

 middle ; dorsal margin elevated in the posterior half ; hinge-line apparently 

 about half the length. The beaks are closely incurved ; umbo rather 

 large and convex ; greatest gibbosity of the shell at about one-third of the 

 length from the anterior extremity and a little above the mid-height. 

 Length of largest specimen seen 13 lines ; height at 5 hnes from the pos- 

 terior extremity 10 lines ; height at the umbones 7 lines ; greatest depth 

 of a single valve 5 lines. Surface unknown but most probably concentri- 

 cally striated. English Head ; H. R. J. Richardson. 



G ? INSULARIS, n. sp. — Sub-ovate ; beaks nearly terminal ; anterior 

 extremity obscurely developed ; ventral margin gently convex ; posterior 

 extremity nearly uniformly rounded ; dorsal margin somewhat straight ; 

 shghtly compressed and elevated, gradually rounded into the posterior 

 margin. Length from the beaks to the middle of the posterior extremity 

 14 lines ; height at one third the length from the same point 11 lines ; 

 depth of both valves about 8 lines. 



Of this species several specimens have been obtained, but they are all 

 in an imperfect state. It has somewhat of the form of an Ambonychia, 



