174 SYSTEMATIC PALEONTOLOGY 



DiPLODONTA HOPKiNSEXsis Clark. 

 Plate XXXYI, Figs. 5, 5a, 6, 7. 



Diploclonta hopMnsensis Clark, 1895, Johns Hopkins Univ. Circ, vol. sv, p. .5. 

 Diplodonta Jiopkhisensis Clark, 1896, Bull. 141, U. S. Geol. Survej', p. 79, pi. xxii, 



figs. la-Id. 

 Diplodonta hopkinsensis Dall, 1900, Trans. Wagner Free Inst. Sci., vol. iii, pt. v, 



p. 1181. 



Description. — " Shell small, suborbicular, globose; surface with fine in- 

 distinct striations; anteriorly and posteriorly rounded." Clark, 1896. 



This species has not been found in Maryland, but as it occurs in the 

 same beds in Virginia it will undoubtedly be found in Maryland later, 

 and for this reason the figures and description are reprinted for the 

 benefit of future investigators. 



Dr. Dall records several localities in the Chickasawan of Alabama. 



Length, 16 mm.; height, 15 mm. 



Occurrence. — Xanjemoy Foematio^^. Evergreen, Va. 



Collection. — Johns Hopkins University. 



Family LUCINIDAE. 



Genus LUCINA Bruguiere. 



LuciN'A AQuiANA Clark. 



Plate XXXVII, Figs. 1, la. 



Lucina aquiana Clark, 1895, Johns Hopkins Univ. Circ., vol. xv, p. 5. 

 Lucina aqioiana Clark, 1896, Bull. 141, U. S. Geol. Survey, p. 78, pi. xx, figs. !«, Ih. 

 (,?) Lucina greggi Harris, 1897, Bull. Amer. Pal. No. 9, p. 70 (In part), pi. xiv, fig. 

 2a (not fig. 2). 



Description. — " Shell of moderate size, somewhat compressed; surface 

 covered with numerous concentric striae; umbones depressed and acumi- 

 nate on account of prominent, deeply incised lunules; anterior side elon- 

 gate; posterior side rounded; hinge with two cardinal and two lateral 

 teeth." Clark, 1896. 



The smaller figure published by Professor Harris of a specimen from 

 Gregg's Landing, Ala., is indistinguishable from this species. 



Length, 18 mm.; height, 18 mm. 



Occurrence. — Aquia Foemation. Aquia Creek, Tipper Marlboro. 



Collections. — U. S. National Museum, Maryland Geological Survey. 



