LAMELLIBRANCHIATA. 391 



Surface marked by fine concentric striae, which are more or less fascicu- 

 late, producing undulations which are more conspicuous on the posterior half 

 of the shell. 



The specimen figured has a length of 27 mm. and a height of 18 mm. 

 Another individual has a length of 25 mm. and a height of 17 mm. 



As compared with E. suhovata the beaks are more anterior, the basal mar- 

 gin is less convex, the umbo is narrower, the umbonal slope more prominent and 

 the post-cardinal slope is wider. 



In tig. 22 of plate Ixiv, the beak is represented as too prominent, giving a 

 disproportionate height to the shell, and the posterior end is too wide.* 



Formation and locality. In the Yellow sandstones, at Burlington, la. 



Edmondia depressa. 



PLATE LXIV, FIG. 32 



EAmondia depreum. Hall. Prelim. Notice Lamellibi-anchiata, 2, p. 91. 1870. 



" " " Pal. N. Y., vol. V, pt. 1. Plates and Explanations : PI. 64, fig. 32. 1883. 



Edtnondiaf tapemfurmU. Mkek. Pal. Ohio, vol. 11, p. 304, pi. 13, fig. 6. 1875. 



Shell large, ovate-elliptical, sub-quadrangular ; length more than one-fourth 

 greater than the height ; basal m.argin gently curving to the post-inferior 

 extremity, where it is abruptly recurved and obliquely sub-truncate above. 

 Cardiniil line straight, scarcely declining posteriorly. Anterior end short and 

 regularly rounded. 



Valves depressed-convex below and posteriorly, and somewhat gibbous 

 above. 



Beaks sub-anterior, moderately prominent (much too prominent, as repre- 

 sented in the figure), slightly inclined forward and rising but little above the 

 hinge-line, Umbonal slope regularly rounded. 



* The figure of E. Burliiuftonenslii, above cited, was made and lithographed about fifteen years since, 

 under the direction of Mr. R. P. Whitfirld, from a specimen then in his collection, and may therefore be 

 considered authentic. The other forms identified by him as of the same species, and thus published in 

 the " Preliminai-y Notice " and " Plates and Explanations," cited above, have, on farther examination, 

 proved to be distinct from that one, and are thus described in this volume. The illustrations on plate xcv 

 will serve to give a more satisfactory expression of the specific characteristics. 



