334 SYSTEMATIC TALEONTOLOGY 



beaks; base nearly straight, ijosterior dorsal slope arcuate, descending; 

 anterior arcnate, beaks low, inconspienous; right valve with the tooth 

 narrow, slender, in a transverse vertical plane, the anterior dorsal 

 margin expanded slightly just in front of it, the scar of the resilium 

 strong, narrow, oblique; left valve with the tooth flattened in a hori- 

 zontal plane, the anterior part longer; interior with faint, obsolete 

 radiations; adductor scars rather large, ovate; margins entire." Dall, 

 1900. 



Length, 8 mm.; height, 5 mm. 



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

 mation. 2 miles south of Governor Eun. Calvert Formation. Plum 

 Point. 



Collection. — Maryland Geological Survey. 



Family SPORTELLID/E. 



Genus SPORTELLA Deshayes. 



Sportella whitfieldi Dall. 

 Plate LXXXVII, Figs. 5a, 5b. 



Syndosmya 'i nuculoides Whitfleld, 1894, Mon. xxiv, U. S. Geol. Survey, y. 81, pi. xv, 



figs. 7-9; not of Conrad. 

 Sportella Whitfieldi DaU, 1900, Trans. Wagner Free Inst. Sci., vol. iii, yt. v, p. 1128. 



Description. — " The shell is rather elongate-ovate, and moderately 

 convex, and extremely thin and delicate in texture. The beak is small, 

 situated rather within the anterior third of the length, behind which 

 the shell is narrowed, tlie posterior end being more narrowly rounded 

 than the anterior; basal and cardinal margins sul)parallel; surface with 

 very fine concentric lines only, and with a very faintly defined, oblique, 

 mesial sulcus. Internally there is a single, moderately strong, direct 

 tooth beneath the beak, with a deep, wide pit in front, in the right valve, 

 and a slight projecting lamellar tooth near its extremity. No appear- 

 ance of a posterior lateral tooth can be seen. Muscular imprints very 

 faint, and a pallial sinus shallow and obscure. It is not an Abra, as 

 there are no lateral teeth." Whitfield. 1894. 



Length, 7.9 mm.; height, 5 mm. 



Occurrence. — ^Calvert Formation. Plum Point. 



Collection. — Maryland Geological Survey. 



