BRACHIOPODS. 55 



Chonetes laevis KEYES. 



Plate xxxvii, figs. 5a-b. 

 Choneles glabra Geinitz, 1866 : Carb. und Dyas in Nebraska, p. 60, tab.iv, 



tigs. 15-18. (Not Hall. 1857.) 

 Chonetes glabra Meek, 1872: U. S. Geol. Sur. Nebraska, p. 171, pi. iv, 



fig. 10; and pi. viii, tigs. 8a-b. 

 Chonetes Icevis Keyes, 1888: Proc. Acad. Nat. Sci., Phila., p. 229, pi. xii, 



figs. 3a-b. 



Chonetes geinitzianus Miller, 1890 : N. A. Geol. and Pal. , p. 339. 

 Chonetes Icevis Keyes, 1891 : Proc. Acad. Nat. Sci., Phila. , p. 246. 



Shell email, thin, transversely semi-elliptic; hinge-line as 

 long as the greatest width of the shell, or often extended be- 

 yond the lateral margins. Ventral valve convex, with a broad, 

 very shallow median depression, which is often wanting en- 

 tirely; beak not prominent, appressed ; cardinal area rather 

 narrow but well defined centrally, becoming linear toward the 

 extremities; foramen moderately wide; cardinal margin bear- 

 ing from four to seven oblique spines on each side of the beak. 

 Dorsal valve flat, or slightly concave; cardinal process small 

 and slightly trilobate. Surface of shell apparently smooth, but 

 under a magnifier it is seen to be marked by numerous very 

 minute concentric lines and more prominent, often somewhat 

 imbricated, lines of growth. 



Horizon and localities. Upper Carboniferous, Upper Coal 

 Measures : Kansas City. 



In the original diagnosis of this species the statement was 

 made that the form was probably the same as that described by 

 Geinitz as Chonetes glabra from the Upper Coal Measures of 

 Nebraska. But inasmuch as Geinitz's name had been preoccu- 

 pied by Hall in 1857 for a species from the Upper Helderberg. 

 Chonetes Icevis becomes the next available name. Miller, how- 

 ever, has proposed still more recently the term Chonetes gei- 

 nitzianus for the same shell, which of course becomes a syno- 

 nym. 



Lately this form has been found in great abundance in 

 central Iowa scattered through a bed of bituminous shale near 

 Des Moines. It is associated with its near congener Ch. mesoloba 

 Norwood & Pratten. The differences between the two species, 



