Maryland Geological Survey 325 



shell anteriorly. Ventral xalxc concave anteriorly, convex near umbo. 

 Umbo small, area narrow, trian^^nlar. Surface with numerous fine striae. 

 Interior of valves pustulose. ]\Iuscular scars unknown. 



Length 3 cm. ; width 3.7 cm. 



This species closely resembles S. pnnctiilifera from which it differs 

 chiefly in its finer stride. 



Occurrence. — Heldeeberg Formation, Keyser Member. Tonoloway. 



Collection. — Maryland Geological Survey. 



[Swartz.] 



Strophonella headleyana (Hall) 

 Plate LIX, Fig. 1-3 



Strophodonta headleyana Hall, 1859, Nat. Hist. N. Y., Pal., vol. ili, p. 185, 

 pi. XX, figs. 1-3, 1861. 



Description. — " Shell nearly semicircular, about three-fourths as long 

 as broad. Ventral valve very concave especially near the front, sometimes 

 depressed convex at the beak ; beak scarcely elevated above the margins of 

 tlie area. Dorsal valve depressed at the umbo, and very convex towards the 

 front: beak not extending beyond the cardinal margin. Hinge-line 

 equalling the greatest width of the shell, crenulated. Area somewhat 

 wide, and marked by transverse stria? produced by the continuation of the 

 crenulations from the hinge-line across the surface. Foramen narrow, 

 closed. 



" Surface marked by coarse sharply elevated stria^, which increase 

 chiefly by implantation, and present a peculiar irregularly waved appear- 

 ance." Hall, 1859. 



A single ventral valve of this species has been collected from Maryland. 

 It was found by Eowe at Corriganville, near Cumberland. There is 

 no need to figure the species in this place, since it has the general expres- 

 sion of S. punctulifera and diifers only in having the sharp striaj wavy 

 in elevation (irregular in height) and more numerous. 



Length 4.6 cm. ; width G.5 cm. 



The writer has in his collection two artificial impressions made from 

 specimens coUectetl by Mr. Andrews in the Upper Oriskany, and now in 



