250 SYSTEMATIC PALEONTOLOGY 



Description. — " P. testa Integra ovali postice oblique recurva, labio pos- 

 tico concavo/' Linne, 1758. 



This species shows great variability, as is testified by the synonyms 

 cited above. 



Length, 28 mm. ; width, 22 mm. 



Occurrence. — St. Mary^s Formation. St. Mary's River, Cove Point. 

 Choptank Formation. Jones Wharf, Greensboro, St. Leonard Creek, 

 Sand Hill. Calvert Formation. Plum Point, 3 miles west of Center- 

 ville. 



Collection. — Maryland Geological Survey. 



Crepidula plana Say. 

 Plate LIX, Figs. 5a, 5b. 



Crepidula plana Say, 1823, Jour. Acad. Nat. Sci. Phila., voL ii, 1st ser., p. 226. 

 Crepidula lamina H. C. Lea, 1843, New Fossil Shells from the Tertiary of Virginia, 



Abst., p. 6. 

 Calyptraa (Crepidula) lamina R. C. Lea, 1845, Trans. Amer. Philos. Soc, vol. ix, 



p. 250, pl. XXXV, tig. 42. [Fide Dall.) 

 Crypta plana Tuomey and Holmes, 1856, Pleiocene Fossils of South Carolina, 



p. Ill, pl. XXV, fig. 12. 

 Crepidula plana Emmons, 1858, Rept. N. Car. Geol. Survey, p. 276, fig. 195. 

 Crypta jAana ? Conrad, 1863, Proc. Acad. Nat. Sci. Phila., vol. xiv, p. 569. 

 Crypta plaiia Meek, 1864, Miocene Check List, Smith. Misc. Coll. (183), p. 16. 

 Crepidtda plana Dall, 1892, Trans. Wagner Free Inst. Sci., vol. iii, pt. ii, p. 358. 

 Crepidula plana ? Whitfield, 1894, Mon. xxiv, U. S. Geol. Survey, p. 124. 



Description. — " Shell depressed, flat, oblong oval, transversely wrinkled, 

 lateral margins abruptly deflected ; apex not prominent, and constituting 

 a mere terminal angle, ol^solete in the old shells ; within white ; diaphragm 

 occupying half the length of the shell, convex, contracted in the middle 

 and at one side. 



" Length 1 and 1-10 of an inch." Say, 1822. 



The forms from Plum Point. differ from the other Maryland forms in 

 possessing a very thick shell. 



Length, 25 mm. ; width, IG mm. 



Occurrence. — St. Mary^s Formation. Cove Point. Choptank For- 

 mation. Jones Wharf. Calvert Formation. Plum Point. 



Collections. — Maryland Geological Survey, Johns Hopkins L'niversity. 



