Wetter — Kinderhook Faunal Studies. 95 



Edmondia aequimarginalis Win. 



PL IV. f. 3. 



Shell subcircular in outline, length, 23 mm., height, 20 mm., 

 greatest convexity of each valve, 6 mm. Beaks central, the 

 anterior and posterior cardinal slopes at right angles with 

 each other. The pallial margin regularly rounded. Surface 

 marked by rather fine concentric striae of growth with an 

 occasional stronger furrow. 



Remarks. This species was originally described as Car- 

 dinia aequimarginalis Win., from Marshall, Michigan. At a 

 later date the species was identified by its author from the 

 " yellow sandstone ' at Burlington, and the species trans- 

 ferred to the genus Edmondia. The specimen here illus- 

 trated and described is the one from which the latter 

 identification was made. It is rather an imperfect specimen 

 which is possibly but a variation of E . nitida. 



Edmondia nitida Win. 



PI. IV. f. 4. 



" Shell small, equi valve, suborbicular, ventricose, slightly 

 oblique, with a subcentral beak. Hinge-line slightly extended 

 posteriorly, obtusely rounded at the extremities ; anterior and 

 posterior sides subparallel ; ventral border circularly rounded, 

 but a little produced in the line of the umbonal ridge. Beak 

 elevated above the hinge, obtuse, slightly incurved ; umbonal 

 ridge making an angle of 08° with the hinge-line; behind this 

 ridge the slope is abrupt to the posterior border; middle por- 

 tion of the shell very slightly flattened from the beak along 

 the region anterior to the umbonal ridge. Surface hand- 

 somely marked by rigid, regular, concentric, raised striae, 

 with a few remote, irregularly-distributed concentric furrows. 

 The striation is preserved in all its sharpness to the very 

 hinge-border." Length of shell, 16 mm., height, 15 mm., 

 convexity of each valve, 5 mm. 



Remarks. This species resembles quite closely some of the 

 illustrations of E. obliqua Hall * from the Chemung fauna in 

 New York, and the two species are certainly closely allied. 



Compare Pal. N. Y. 5 1 . pi. 64. f. 16. 



