INVERTEBRATES. 347 



It is with considerable hesitation that we refer this species, even with a. 

 query, to Phillips's unioniformis. It certainly looks so unlike his figure that 

 we should scarcely have thought even a comparison necessary, had it not been 

 that Prof, de Koninck very positively identifies with Phillips's species, after a 

 direct comparison with authentic English specimens, a form differing but 

 slightly from our shell. Prof, de Koninck's figures represent a form rather more 

 gibbous, and more rounded in outline behind, than that figured by us, but some 

 of our specimens, not figured, agree more nearly with his in these characters. 

 Unless the E. unioniformis is a very variable shell, we should think it entirely 

 distinct from ours, as well as from that figured by Prof, de Koninck. 



Dr. Geinitz refers a shell to Panopsea, from the Permian rocks of Germany, 

 somewhat like ours, but agreeing much more nearly with Prof, de Koninck's 

 figures. (See P. lunulata, G. — JDyas, p. 58, pi. xii, fig. 22.) We cannot be- 

 lieve, however, that such a form can be properly referred to Panopsea, nor can 

 we agree with those who refer to that genus any palaeozoic species. 



Prof. Swallow has described, in the Transactions of the St. Louis Academy 

 of Sciences, several species from Kansas, under the names Edmondia and Car- 

 diomorpha?, some one of which may be identical with our shell, but as he has 

 only published rather brief descriptions, without figures, we have not the means 

 of satisfactorily determining this point. 



Our figure is from an internal cast, and shows the impression (fig. 6 and 6 a) 

 of the internal cartilage plate. 



Locality and position : North branch of Saline creek, Gallatin county, Illi- 

 nois; Upper Coal Measures. 



Genus PLEUROPHORUS, King, 1844. 



(Ann. Mag. Nat. Hist., xiv, p. 313.) 



Pleurophorus subcostatus, M. and W. 



PI. 27, fig. 2 and 2 a. 



Pleurophorus subcostatus, Meek and Worthen, Dec, 1865. Proceed. Acad. Nat. Sci., 

 Philad., p. 246. 



Shell elongate-oblong, moderately convex; umbonal ridges 

 the most convex part of the valves, and extending obliquely 

 from the beaks towards the postero-basal margin; anterior 

 ventral region somewhat compressed ; basal and cardinal mar- 

 gins very nearly straight and subparallel, the former being 



