230 POTTS VILLE FAUNA OP OHIO 



Lower Mercer limestone has the following measurements : height 27 mm , 

 length of hinge line 23 mm., greatest width below hinge line 29 mm. 

 Horizon and locality. Boggs limestone: Muskingum County, Lo- 

 cality 26, c. Widely distributed in the Lower Mercer member, a. 

 Upper Mercer member: Muskingum County, Locality 68, r; Mahoning 

 County, Locality 76, r. Widely distributed throughout the McArthur 

 member, c. 



Genus Crenipecten Hall 



Crenipecten foerstii Herrick 

 PI. XIII, figs. 7, 8 



1887 Crenipecten foerstii. Herrick, Bull. Den. Univ., Vol. 2, p. 28, PL 3, Figs. 9, 9a. 

 Coal Measures: Flint Ridge, Ohio. 



Herrick' s description. "Shell below the ears subcircular, but 

 moderately convex, equi valve. Right valve with anterior ear pro- 

 duced, rounded in front, separated from the valve by a deeply im- 

 pressed, concave auricular sinus; posterior ear nearly rectangular, 

 slightly concave in posterior outline, separated from the valve by an 

 impressed line; hinge line one-half the height of the valves. Left 

 valve of same form, but the ears less distinctly separated; hinge line 

 less than one-half the height, anterior ear with concave front outline. 

 The beaks are acute and moderately prominent. Surface marked by 

 numerous close, minute, concentric lines, and numerous irregular, con- 

 centric wrinkles which give a peculiar appearance to the shell, not 

 shared by other species. These wrinkles are less marked on young 

 shells. There are also, in most cases, indications of radiating lines, 

 which in the larger shells are strong striae or ribs, at a distance from 

 each other." 



This species appears in the Boggs limestone where it is rare; but 

 in the Lower Mercer horizon it constitutes an abundant and character- 

 istic fossil, especially in the Flint Ridge region. Herrick states that 

 next to Entolium aviculatus Swallow it is the most common bivalve 

 at Flint Ridge, which statement in the experience of the writer is true. 

 A specimen a little above average size measures: length 20 mm., height 

 20.5 mm., length of hinge line of right valve 11 mm. 



Horizon and locality. Boggs limestone : Muskingum County, Lo- 

 cality 27, r. Widely distributed in the Lower Mercer limestone, a. 

 Upper Mercer: Holmes County, Locality 73, r. McA-rthur limestone: 

 Vinton County, Locality 85, r. 



