310 SYSTEMATIC PALEONTOLOGY 



valve, and has a comparatively small groove beneath the reflected edge; 

 ribs quite irregular in size and variable in number, usually about hve. 



Length, 23 mm. ; height, 18 mm. ; diameter, 6.5 mm. 



Occurrence. — Choptank Formation. Greensboro. Calvert For- 

 mation. Fairhaven, Chesapeake Beach, 3 miles south of Chesapeake 

 Beach, Plum Point, Lyon's Creek, Eeed's, JeAvell. 



Collections. — Maryland Geological Survey, Johns Hopkins University. 



Chione parkeria n. sp. 

 Plate LXXVI, Figs. 9, 10, 11. 



Description. — Shell triangular, depressed, posteriorly somewhat cunei- 

 form, anteriorly rounded; beaks projecting, acute, approximate; lunule 

 distinct, cordate ; base posteriorly emarginate ; dorsal surface with about 

 five to eight concentric ribs so perfectly flattened and closely appressed to 

 the valve and each other as to become almost obsolete and be marked 

 only by faint undulations and fine concentric impressed or laminated 

 lines ; ribs crossed from beak to base by numerous distinct, regular, radi- 

 ating lines ; cardinal teeth three in each valve ; laterals none ; muscle im- 

 pressions deep ; pallial sinus a slight notch ; margin minutely crenulated. 

 This species seems to be closely related to C. ulocyma Ball. 



Length, 29 mm.; height, 23 mm.; diameter, 8 mm. 



Occurrence. — Calvert Formation. Parker Creek, 2 miles south of 

 Parker Creek. 



Collections. — Maryland Geological Survey, Johns Hopkins University. 



Chione alveata (Conrad). 

 Plate LXXVI, Figs. 1, 2, 3. 



VemiR alveata Conrad, 1831, Jour. Acad. Nat. Sci. Phila., vol. vi, 1st ser., p. '2(J4, 



pi. xi, ligs. 14, 15. 

 Venus alveata Conrad, 1838, Fossils of the Medial Tertiary, p. 9, pi. v, tig. 2. 

 Oircumphalus alveatus Conrad, 1863, Proc. Acad. Nat. Sci. Phila., vol. xiv, p. 575. 

 Chione {LiropJiora) alveatus Meek, 1864, Miocene Check List, Smith. Misc. Coll. 



(183), p. 9. 

 Chione (Lirophora) alveata Dall, 1903, Trans. Wagner Free Inst. Sci., vol. iii, pt. vi, 



p. 1298. 



Description. — " Shell subtriangular, thick, with about six, much ele- 

 vated, very thick and profoundly reflected concentric ribs, remote, and 



