278 SYSTEMATIC PALEONTOLOGY 



Panopea AMERICANA Coiiracl. 

 Plate LXYI, Fig. 2. 



Panoptea Americana Conrad, 1838, Fossils of the Medial Tertiary, i). 4, pi. ii, tig. 1. 

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

 Panopcea Americana Meek, 1804, Miocene Check List, Smith. Misc. Coll. (183), p. 12. 

 Panopea americana Dall, 189S, Trans. Wagner Free Inst. Sci., vol. iii, pt. iv,p. 830. 



Description. — " Shell rhomboidal, flexuoiis, 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 Formation. Governor Eun (upper and 

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

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

 Peach Blossom Creek, Cordova, Greensboro. Calvert Formation. 

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



Collections. — Maryland Geological Survey, Johns Hopkins University. 



Genus SAXICAVA Fieuiiau de Beilevue. , 



Saxicava arctica (Linne). 

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



Mya arctica Linne, 1767, Syst. Nat., 12th Edit., p. 1118. 



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



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



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



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



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



Saxicava hilineata 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, 186'.t, Amer. Jour. Conch., vol. v, j). 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. 



