MARYLAND GEOLOGICAL SURVEY 343 



Superfamily CARDITACEA. 

 Family CARDITID/E. 



Genus CARDITA (Bruguiere) Lamarck. 

 Section CARDITAMERA Conrad. 



Cardita protracta (Conrad). 

 Plate XCI, Figs. 4, 5, 6. 



Carditamera protracta Conrad, 1843, Proc. Acad. Nat. Sci. Phila., vol. i, p. 30.5. 

 Carditamera protracta Conrad, 184.5, Fossils of the Medial Tertiary, p. 65, pi. xxxvii, 



flg. 2. 

 Cardita protracta d'Orbigny, 18.52, Prod. Pal. Strat., vol. iii, p. 114, No. 2134. 

 Carditamera protracta Conrad, 1863, Proc. Acad. Nat. Sci. Phila., vol. xiv, p. 579. 

 Carditamera aculeata Conrad, 1863, Proc. Acad. Nat. Sci. Phila., pp. 578, 585. 

 Carditamera protracta Meek, 1864, Miocene Check List, Smith. Misc. Coll. (183), p. 7. 

 Carditamera aculeata Meek, 1864, Miocene Check List, Smith. Misc. Coll. (183), p. 7. 

 Carditamera recta Conrad, 1869, Amer. Jour. Conch., vol. iv, p. 279, pi. xx, fig. 2. 

 Carditamera aculeata Whitfield, 1894, Mon. xxiv, U. S. Geol. Survey, p. 58, pi. ix, 



figs. 7, 8. 

 Cardita (Carditamera) recta Dall, 1903, Trans. Wagner Free Inst. Sci., vol. iii, pt. vi, 



p. 1413. 

 Cardita (Carditamera) protracta Dall, 1903, Trans. Wagner Free Inst. Sci., vol. iii, 



pt. vi, p. 1414. 



Description. — " Trapezoidal, elongated, compressed, widely contracted 

 from beak to base; dorsal and basal margins nearly parallel; ribs about 

 15, the middle ones triangular and crenated; posterior ribs rounded and 

 having distant, arched, squamose, coarse striiae; summit of the beaks 

 scarcely prominent above the hinge line." Conrad, 1843. 



There seems to be no sufficient ground for separating the Maryland 

 Miocene Carditamera^. They show a gradual decrease in the number 

 of ribs from forms with about nineteen to twenty-one in the earlier 

 deposits, as at Church Hill, to forms with fifteen to seventeen in later 

 deposits, as at Jones Wharf. Occasionally a specimen is rather j^ro- 

 longed, or slightly thicker, or is not so widely contracted from beak to 

 base, but these variations all seem too slight to be considered of even 

 varietal value. The C. aculeata is merely a young form. C. recta is 

 not more prolonged than many a Governor Eun specimen of C. pro- 

 tracta. C. carinata, first described from jSTewbern, N". C, is listed by 

 Conrad from Dover Bridge — the Choptank near Easton. If his identi- 

 fication were not wrong, then it is probable that C. carinata should be 

 united with C. protracta and take precedence of the latter name. 



