MARYLAND GEOLOGICAL SURVEY 309 



cated, direct, and remote from the line of the base; basal margin pro- 

 foundly curved; lunule dilated, cordate, defined by a groove, and not dis- 

 tinctly impressed ; inner margin finely crenulated. 



" This shell is of a more rotund, tumid form than any of the species 

 allied to V. mercenaria, and much more capacious ; the lunule is shorter 

 and wider." Conrad, 1843. 



The markedly anterior position of the beak, the compact, rounded out- 

 line and the prominent, square truncation of the posterior extremity serve 

 to distinguish this from other forms. 



This variety is probably the ancestor of var. mortoni of the St. Mary's 

 formation as it is practically indistinguishable from the young of that 

 form. 



Length, 62 mm. ; height, 43 mm. ; diameter, 18 mm. 



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

 of Governor Run, Flag Pond, Jones Wharf, Turner, Pawpaw Point, Peach 

 Blossom Creek, Cordova, Greensboro, Dover Bridge. 



Collections. — Maryland Geological Survey, Johns Hopkins University. 



Genus CHIONE Megerle von Miihlfeld. 



Chione latilirata (Conrad). 

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



Venus latilirata Courad, 1841, Proc. Acad. Nat. Sci. Phila., vol. i, p. 28 



Not Venus latilirata Tuomey and Holmes, 1856. 



Venus latilirata Conrad, 1845, Fossils of the Medial Tertiary, p. 68, pi. xxxviii, 



fig. 3. 

 Circumphalus latlliratns Conrad, 1863, Proc. Acad. Nat. Sci. Phila., vol. xiv, p. 575. 

 Chione (Lirophora) latilirata Meek, 1864, Miocene Check List, Smith. Misc. Coll. 



(183), p. 9. 

 Chione [Lirophora) latilirata Dall, 1903, Trans. Wagner Free Inst. Sci., vol. iii, pt. 



vi, p. 1298, pi. xlii, tig. 3. 



Description. — " Trigonal, convex depressed, ribs concentric, about 5 

 or 6 in number, flattened, reflected, irregular, one of them generally very 

 wide ; ribs irregularly sulcated on the posterior slope ; inner margin finely 

 crenulated. Smaller than V. alveata, and with broader, less prominent 

 ribs, which do not diminish in size on the posterior margin." Conrad, 

 1841. 



Often the reflected portion is broadly adherent or well plastered to the 



