Del topee ten occiden tails (Shumard) 



1855 Pecten occidentalis. Shumard, Geol. Rep. Mo., p. 207, PI. C, Fig. 18. 

 Coal Measures: Near Plattsburg, Clinton County, Missouri. 



Description. This common and widely distributed Pennsyl- 

 vanian pelecypod appears in this State in the Boggs limestone and 

 continues as a common fossil throughout the remainder of the Potts- 

 ville formation. It is recognized by its subequal ears and its rounded 

 radiating ribs of unequal size which die out at various intervals be- 

 tween the beak and margins with only a comparatively few reaching 

 the beak. The Ohio specimens are apparently smaller than is gen- 

 erally the case; an individual of average size from the Boggs limestone 

 measures: length 20 mm., width 18 mm., length of hinge line 15 mm. 



Horizon and locality. Boggs limestone: Blunt Run, Muskingum 

 County (Locality 27), r; common throughout the middle and upper 

 members of the Pottsville formation. 



Genus Acanthopecten Girty 

 Acanthopecten carboniferous (Stevens) 



1858 Pecten carboniferous. Stevens, Am. Jour. Sci. and Arts, Vol. XXV, p. 261. 

 Coal Measures: Crooked Creek, Marion County, Illinois. 



Description. This is an abundant and widely distributed fossil 

 in the Pottsville rocks above and including the Boggs member, but 

 it has not been discovered below the latter formation. It is readily 

 distinguished by its large ears, and by its distinctive surface markings 

 of 15 to 18 large, regular plications which are marked at regular, 

 somewhat distant intervals by spine-like projections where concentric 

 lines cross the plications. The size is comparatively constant: an 

 individual of average size measures: height 16 mm; length of hinge 

 line 13 mm.., greatest width below hinge line 18 mm. A specimen of 

 unusual size from the Lower Mercer limestone has the following 

 measurem.ents : height 27 mm., length of hinge line 23 rcrfm., greatest 

 width below hinge line 29 mm. 



Horizon and locality. Boggs limestone: near Hopewell P.O., 

 Muskingum County (Locality 26), c. Abundant and generally 

 distributed in the Lower Mercer and higher horizons. 



Genus Crenipecten Hall 

 Crenipecten foerstii Herrick 



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

 Coal Measures: Flint Ridge, Ohio. 



Herrick's description: "Shell below the ears subcircular, but mod- 

 erately convex, equivalve. Right valve with anterior ear produced, 

 rounded in front, separated from the valve by a deeply impressed, 

 concave auricular sinus; posterior ear nearly rectangular, slightly 

 concave in posterior outline, separated from the valve by an im- 



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