Explanation of Plate 25 



Figs. 1, 2. — Mya truncata Linnaeus: 1, a typical .1/. truncata from Puget Sound, Wash.; 



2, from Point Barrow, Alaska, with a shorter posterior end and differently shaped sinus. 

 Fig. 3. — Mya truncata var. uddevallensis Forbes from Point Barrow, Alaska, showing the 



very short posterior end and the resulting shallow sinus, also the oblique truncation 



that makes the ventral posterior end shorter than the dorsal. 

 Fig. 4. — Mya pseudoarenaria Schlesch from Point Barrow, Alaska (Eluitkak Pass, 40 feet). 



showing the rounded posterior end, with a sinus similar to that of a typical .1/. truncata. 

 Fig. 5. — Mya arenaria Linnaeus from Alonterey Bay (Moss Landing), Calif., showing the 



deep sinus, the ventral line of which is not confluent with the pallial line. 

 Figs. 6, 8. — Panomya arctica (Lamarck): 6, from off Cape Cod, Mass.; 8, from Point 



Barrow, Alaska, shell broken at the hinge. 

 Fig. 7. — Panomya ampla Dall from Captain's Bay, Amaknak Island, Alaska, showing the 



pointed anterior and flaring posterior end. This specimen is squarely truncate but 



the majority are obliquely truncate in a direction opposite to that of P. arctica (see 



figs. 6, 8). 

 Magnification: All X .74. 



