MARYLAND GEOLOGICAL SURVEY 289 



" Three and a quarter inches in length and f onr and a quarter inches 

 in breadth. The cardinal pit is large, thick, and subcordate, and the lat- 

 eral teeth are short and very robust; when the valves are closed, the de- 

 pression on the anterior slope forms a slightly concave area." Conrad, 

 1830. 



Length, 108 mm.; height, 86 mm.; diameter, 28 mm. 



Occurrence. — St, Mary's Formation. Cove Point, St. Mary's Eiver. 



Collections. — Maryland Geological Survey, Johns Hopkins University, 

 U. S. National Museum. 



Spisula (Hemimactra) confraga (Conrad). 

 Plate LXX, Figs. 5a, 5b. 



Macira confraga Conrad, 1833, Amer. Jour. Sci., vol. xxiii, p. 340, not spelled co7i- 



fragosa. 

 Mactra fragosa Conrad, 1838, Fossils of the Medial Tertiary, p. 26, pi. xiv, flg. 2. 

 Mactra incrassata Conrad, 1838, Fossils of the Medial Tertiary, p. 24, pi. xiii, fig. 2. 

 Mesodesma confraga Conrad, 1863, Proc. Acad. Nat. Sci. Pbila., vol. xiv, p. 574. 

 Mesodesma incrassata Conrad, 1863, Proc. Acad. Nat. Sci. Phila., vol. xiv, p. 574. 

 Spisula confragosa Meek, 1864, Miocene Check List, Smith. Misc. Coll. (183), p. 11. 

 Spisula confragosa Dall, 1898, Trans. Wagner Free lust. Sci., vol. iii, pt. iv, p. 900. 



Description. — "Shell subtri angular; narrow, somewhat thick, with 

 coarse concentric lines; umbo oblique; beaks a little elevated, approxi- 

 mate ; posterior side longer and less obtuse than the anterior ; f osset large 

 cordate, oblique ; lateral teeth strong ; muscular impressions large. Length 

 two inches." Conrad, 1833. 



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

 Formation. Governor Eun, Jones Wharf, Cordova, Sand Hill. Cal- 

 vert Formation. Chesapeake Beach. Seed's. 



Collections. — Philadelphia Academy of Natural Sciences, Maryland 

 Geological Survey, Johns Hopkins University. 



Spisula (Hemimactra) subparilis (C-onrad). 

 Plate LXX, Figs. 6a, 6b. 



Mactra subparilis Conrad, 1841, Amer. Jour. Sci., vol. xli, p. 346, pi. ii, flg. 13. 

 Mactra subparilis Conrad, 1845, Fossils of the Medial Tertiary, p. 69, pi. xxxix, 



flg. 4. 

 Standella subparilis Conrad, 1863, Proc. Acad. Nat. Sci. Phila., vol. xiv, p. 573. 

 Standella subparilis Meek, 1864, Miocene Check List, Smith. Misc. Coll. (183), p. 11. 

 Spisula {Mactromeris) subparilis Dall, 1898, Trans. Wagner Free Inst. Sci., vol. iii, 



pt. iv, p. 900. 

 19 



