280 SYSTEMATIC PALEONTOLOGY 



Description. — " Shell subtriangular, convex, thick, obscurely undu- 

 lated; with a fold on the posterior submargin and the extremity angu- 

 lar; basal margin acute; cardinal tooth very thick and elevated. Length, 

 one inch." Conrad, 1833. 



Surface of left valve with obsolete concentric undulations, angular 

 posteriorly; right valve with irregular, concentric undulations, beak 

 more prominent and strongly curved than in lower valve ; posterior sub- 

 margin ridged, tooth massive. 



Leng-th, 34 mm.; height, 29 mm.; diameter, 13 mm. 



Occurrence. — Choptank Fokmation. Governor Eun, 2 miles south 

 of Governor Eun, Flag Pond, Jones Wharf, Cuckold Creek, Turner, 

 Pawpaw Point, Dover Bridge, Peach Blossom Creek, Trappe Landing, 

 Cordova, Greensboro, Skipton. Calvert Formation. Chesapeake 

 Beach, 3 miles south of Chesapeake Beach, Plum Point, Eeeds. 



Collections. — Maryland Geological Survey, Johns Hopkins University. 



Section ALOIDIS Megerle von MUhlfeld. 



CoRBULA ELEVATA Conrad. 



Plate LXVII, Figs. 4, 5. 



Corbula elevata Conrad, 1838, Fossils of the Medial Tertiary, p. 7, pi. iv, tig. 8. 

 Corbula elevata Conrad, 1863, Proc. Acad. Nat. Sci. Phila., vol. xiv, p. 572. 

 Corbula elevata Meek, 1864, Miocene Check List, Smith. Misc. Coll. (183), p. 12. 

 Corbula curta Conrad, 1867, Amer. Jour. Conch., vol. iii, p. 269, pi. xxi, figs. 6-8. 

 Corbula (Aloidis) elevata Dall, 1898, Trans. Wagner Free Inst. Sci., vol. iii, pt. iv, 

 p. 8.52. 



Description. — " Shell triangular, equilateral, height greater than the 

 length; inferior valve ventricose, with regular numerous concentric 

 impressed lines, which disappear on the posterior slope; umbo pro- 

 foundly elevated ; posterior slope with an obtuse furrow descending from 

 the beak ; extremity narrowed, slightly emarginate." Conrad, 1838. 



Length, 12 mm.; height, 12.5 mm.; diameter, 4.5 mm. 



Occurrence. — Calvert Formation. Fairhaven, Chesapeake Beach, 

 3 miles south of Chesapeake Beach, Plum Point, Lyon's Creek, Tru- 

 man's Wharf, White's Landing, Eeeds, 3 miles west of Centerville. 



Collections. — Maryla.nd Geological Survey, Johns Hopkins University, 

 U. S. ;N"ational Museum. 



