366 SYSTEMATIC PALEONTOLOGY 



Genus MODIOLUS Lamarck. 



Modiolus ducatelii Conrad. 



Plate XCVII, Figs. 6, 7. 



Modiola Ducatellii Conrad, 1840, Fossils of the Medial Tertiary, p. 53, pi. xxviii, 



fig. 2. 

 Perna Ducatellii Conrad, 1863, Proc. Acad. Nat. Sci. Phila., vol. xiv, p. 579. 

 Volsella Ducatellii Meek, 1864, Miocene Check List, Smith. Misc. Coll. (183), y. 7. 

 Modiolus Ducatelii Dall, 1898, Trans. Wagner Free Inst. Sci., vol. iii, pt. iv, u. 793. 



Description. — " Shell profouiidly elongated, ventricose, valves con- 

 tracted obliquely from the apex to the middle of the basal margin; lines 

 of growth coarse and prominent; extremity of hinge line salient and 

 rounded; posterior extremity regularly rounded; anterior extremity 

 rather prominent and pointed." Conrad, 1840. 



This shell is rarely found entire. But its identification should give no 

 difficulty, especially if the beak is present. 



Length, 133 mm.; width, 55 mm.; diameter, 21 mm. 



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

 mation. Governor Eun, 2 miles south of Governor Kun, Jones Wharf, 

 Turner, Dover Bridge, Cordova. Calvert Formation. Chesapeake 

 Beach, 3 miles south of Chesapeake Beach, Plum Point, Eeed's. 



Collections. — Maryland Geological Surve}', Johns Hopkins University, 

 Maryland Academy of Science, IT. S. National Museum. 



Section GREGARIELLA Monterosato. 



Modiolus virginicus (Conrad). 

 Plate XCVII, Figs. 8a, 8b. 



Modiolaria virginica Conrad, 1867, Amer. Jour. Conch., vol iii, p. 267, pi. xxii, 



tig. 3. 

 Modiolaria virginica Dall, 1898, Trans. Wagner Free Inst. Sci., vol. iii, pt. iv, p. 806. 



Description. — " Oblong, subarcuate, ventricose anterior side without 

 radiating lines; umbonal slope raised, rounded with close, crenulated, 

 radiating lines, extending to the posterior margin and disposed to l)i fur- 

 cate towards the base; beaks nearly terminal." Conrad, 1867. 



In front of the smooth area extending from the umbonal area to the 

 ventral margin there is a small area near the beak with radiating crenu- 

 lated lines; edge of valve finely beaded; dorsal margin not angular but 

 curved. 



