MARYLAND GEOLOGICAL SURVEY 339 



Subgenus LUCINOMA Dall. 



Phacoides (Lucinoma) contractus (Say). 

 Plate XC, Figs. 5, 6. 



Lucina contracta. Say, 1824, Jour. Acad. Nat. Sci. Phila., vol. iv, 1st sen, p. 145, 



pi. X, fig. 8. 

 Lucina. contracta Conrad, 1840, Fossils of the Medial Tertiary, p. 40, pi. xx, flg. 5. 

 Lucina subplanata Conrad, 1841, Proe. Acad. Nat. Sci. Phila., vol. i, p. 29 (young). 

 Lucina subplanata Conrad, 1842, Jour. Acad. Nat. Sci. Phila., vol. viii, 1st ser., 



p. 184. 

 Lucina contracta Tuomey and Holmes, 18.56, Pleiocene Fossils of South Carolina, 



p. 54, pi. xviii, tig. 1. 

 Lucina contracta Conrad, 1863, Proe. Acad. Nat. Sci. Phila., vol. xiv, p. 577. 

 Lucina subplanata Conrad, 1863, Proe. Acad. Nat. Sci. Phila., vol. xiv, p. 577. 

 Lucina contracta Meek, 1864, Miocene Check List, Smith. Misc. Coll. (183), jj. 8. 

 Lucina subplana Meek, 1864, Miocene Check List, Smith. Misc. Coll. (183), p. 8. 

 Phacoides [Lucinoma) contractus Dall, 1903, Trans. Wagner Free Inst. ScL, vol. iii, 



pt. vi, p. 1380. 



Description.- — "Sliell convex, suborbicular, with niTiuerous, concentric, 

 regular, equidistant, elevated, membranaceous striae, and intermediate 

 smaller transverse lines: umdones not very prominent: apices proximate, 

 nearly central : anterior hinge margin rectilinear, to an obtuse angle near 

 the middle of the anterior margin: anterior suhmargin with a very 

 slightly impressed line : posterior margin rounded : cardinal teeth one 

 in the left valve, and two in the right, the posterior one of which is 

 subbifid at tip : lateral teeth none : within obsoletely striated towards the 

 margin : posterior muscular impression perfectly rectilinear, elongated, 

 and oblique." Say, 1824. 



Easily distinguished by the elevated, concentric lamellae. An im- 

 pressed line extends from the beaks to the posterior margin; shell thin 

 and rather fragile. 



Length, 42 mm.; height, 39 mm.; diameter, 5.9 mm. 



Occurrence. — St, Mary's Formation. St. Mary's River. Choptank 

 Formation. Governor Run, 2 miles south of Governor Run, Flag Pond, 

 Pawpaw Point, Jones Wharf, Greensboro, Cordova. Calvert Forma- 

 tion. Fairhaven, Lyon's Creek, 3 miles south of Chesapeake Beach, 

 Plum Point, Jewell. 



Collections. — Maryland Geological Survey, Johns Hopkins University. 



