194 SYSTEMATIC PALEONTOLOGY 



Family MYAC1DAE. 



Genus MY A (Linne) Lamarck. 

 Mya arenaria Linne. 



Plate LIU, Figs. 5, 6; Plate LIV, Figs. 1-4. 



Mya arenaria Linne, 1758, Syst. Nat. ed. x, p. 670. 



Mya arenaria Holmes, 1858, Post-Pi. Fos. S. C, p. 55, pi. viii, fig. 15. 



Mya arenaria Dall, 1889, Bull. U. S. Nat. Mus., No. 37, p. 70, pi. xlix, fig. 9, 



pi. lv, fig. 2; pi. lxi, fig. 2. 

 Mya arenaria Dall, 1898, Trans. Wagner Free Inst. Sci., vol. iii, pt. iv, 



p. 857. 



Description. — " M. testa ovata postice rotundata, cardinis dente an- 

 trorsum porectus rotnndata denticuloqne later ali." Linne, 1758. 



This species makes its first appearance in the Miocene of Virginia and 

 Massachusetts (Gay Head) but has never been found in the Maryland 

 Miocene where it is represented by M. producta a quite distinct form. It 

 has not been observed in the Atlantic Coast Pliocene, but in the Pleisto- 

 cene ranges from Labrador to South Carolina and in the Eecent from 

 Nova Scotia to North Carolina. Although not indigenous to the Pa- 

 cific, since its accidental introduction into Californian waters, it has 

 flourished and spread rapidly. 



Width, 108 mm. ; height, 68 mm. 



Occurrence. — Talbot Formation. Wailes Bluff near Cornfield Har- 

 bor, and Langleys Bluff, St. Mary's County. 



Collections. — Maryland Geological Survey, Johns Hopkins University, 

 and TJ. S. National Museum. 



Superfamily MACTRACEA. 



Family MACTRIDAE. 



Subfamily MACTR1NAE. 



Genus MULINIA Gray. 



Mulinia lateralis (Say). 

 Plate LV, Figs. 1-4. 



Mactra lateralis Say, 1822, Jour. Acad. Nat. Sci. Phila., vol. ii, 1st ser„ 



p. 309. 

 Mactra lateralis Holmes, 1859, Post-Pi. Fos. S. C, p. 40, pi. vii, fig. 9. 

 Mactra lateralis Dall, 1889, Bull. U. S. Nat. Mus., No. 37, p. 62, pi. lxix, fig. 8. 

 Mulinia lateralis Dall, 1898, Trans. Wagner Free Inst. Sci., vol. iii, pt. iv, 



p. 901. 



