278 SYSTEMATIC PALEONTOLOGY 



Panopea AMERICANA Coiiracl. 

 Plate LXVI, Fig. 2. 



Panopcea Americana Conrad, 1838, Fossils of the Medial Tertiary, p. 4, pi. ii, fig. 1. 

 Olycimeris Americana Conrad, 1863, Proc. Acad. Nat. Sci. Phila., vol. xiv, p. .571. 

 Panopcea Americana Meek, 1864, Miocene Check List, Smith. Misc. Coll. (183), p. 12. 

 Panopea americana Dall, 1898, Trans. Wagner Free Inst. Sci., vol. iii, pt. iv, p. 830. 



Description. — " Shell rliomboidal, fiexuous, profoundly gaping at both 

 extremities; surface undulate with coarse lines of growth; anterior mar- 

 gin obliquely truncated, nearly parallel with the posterior margin, which 

 is also oblique and truncated; basal margin contracted in the middle; 

 cardinal process very prominent and slender; nympha profound and 

 very thick, its upper surface transversely striated; right valve with a 

 wide and profound cardinal fosset." Conrad, 1838. 



This species is very abundant, large, and well preserved in the Chop- 

 tank formation. 



Length, 190 mm. ; width, 102 mm. ; diameter, 34 mm. 



Occurrence. — Choptank roRMATiON. Governor Eun (upper and 

 lower beds), 2 miles south of Governor Kun (upper and lower beds), 

 Flag Pond, St. Leonard Creek, Jones AVharf, Turner, Pawpaw Point, 

 Peach Blossom Creek, Cordova, Greensboro. Calvert Formation. 

 3 miles south of Chesapeake Beach, Reeds, Wye Mills, Lyon's Creek. 



Collections. — Maryland Geological Survey, Johns Hopkins University. 



Genus SAXICAVA Fleuriau de Bellevue. 

 S.A.XICAVA ARCTiCA (Linue). 



Plate LXVI, Figs. 3, 4, 5, 6. 



3fya arciica Linne, 1767, Syst. Nat., 12th Edit., p. 1113. 



Mya arctica Fabricius, 1780, Fauna Gronlandica, p. 407. 



Saxicava distorta Say, 1822, Jour. Acad. Nat. Sci. Phila., vol. ii, 1st ser., p. 318. 



Saxicava bilineata Conrad, 1838, Fossils of the Medial Tertiary, p. 18, pi. x, fig. 4. 



Saxicava distorta Gould, 1841, Invert. Mass., p. 61, fig. 40. 



Saxicava bilineata Conrad, 1863, Proc. Acad. Nat. Sci. Phila., vol. xiv, p. 571. 



Saxicava bilineata Meek, 1864, Miocene Check List, Smith. Misc. Coll. (183), p. 12. 



Saxicava insita Conrad, 1869, Amer. Jour. Conch., vol. v, p. 40. 



Saxicava incita Conrad, 1869, Amer. Jour. Conch., vol. v, jl 101. 



Saxicava arctica Gould (Binney's), 1870, Invert. Mass., p. 89. 



Saxicava arctica Dall, 1898, Trans. Wagner Free Inst. Sci., vol. iii, pt. iv, p. 834. 



