Saxicava rugosa Lam. (= arclica L.) 



Fig. i Recent specimen (right valve) from Barden bay, Greenland. 



Fig. 2 Outlines of right valves showing comparison in size of the largest Pleisto- 

 cene specimens from various localities in Canada and New York with one of the 

 largest recent specimens, a, recent', Barden bay; b, Montreal; c, Valcour island; 

 d, Port Kent; e, Willsboro; /, Ottawa vicinity; g, few miles north of Port Henry. 



Fig. 3 Similar outlines of average-sized specimens showing comparison with 

 a medium-sized recent form, a, recent, Barden bay; b, Montreal; c, Valcour 

 island; d, Port Kent (Ottawa and vicinity about the same); e, Willsboro. 



Fig. 4, 5 Two specimens from Montreal showing the remarkable thickness of 

 the shells. Both valves are weathered. 



Macoma groenlandica Beck (= balthica L.) 

 Fig. 6 Recent specimen (left valve) from the New York coast. 

 Fig. 7 Outlines of left valves showing comparison in size of the largest Pleisto- 

 cene specimens from various localities in Canada and New York with one of the 

 largest recent specimens, a, recent, South Amboy, N. J.; b, Montreal; c, Port 

 Kent (Burlington vicinity and Lapham Corners practically the same); d, Cumber- 

 land Head (Port Henry practically the same); e, Willsboro (Valcour island 

 and Essex practically the same); /, Chimney Point; g, Crown Point. 



Fig. 8 Similar outlines of average-sized specimens, a, recent, Cape May, 

 N. J.; b, Montreal; c, Valcour island (Burlington and Lapham Corners about 

 the same); d, Cumberland Head; e, Port Kent (Willsboro, Essex, Port Henry 

 practically the same); /, Chimney Point; g, Crown Point. 



