102 Trans. Acad. Sci. of St. Louis. 



latter species is represented by a single specimen which is 

 much larger than those from the Chonopectus sandstone, 

 with a more triangular form and with a much more angular 

 umbonal ridge. Judging from his description and the meas- 

 urements given, Winch ell considered this larger specimen as 

 the principal type of his species, and it is therefore retained 

 as the type of Oardiomorpha or rather Schizodus irigonalis. 

 The smaller species from the Chonopectus sandstone requires 

 a new name, 8. iowensis being here proposed. This species 

 may be compared with 8. gregarius Hall, from the New York 

 Chemung fauna, but it is shorter than that species. It also 

 resembles 8. cuneus Hall, from the Waverly series in Ohio. 



Schizodus burlingtonensis n. sp. 



PL IV. f.l5. 



Shell subovate in outline, depressed convex, length, 18 mm. 

 and breadth, 11 mm. Hinge-line short; anterior margin regu- 

 larly rounded ; ventral margin nearly straight posteriorly, but 

 curving upward in the anterior half; posterior margin sharply 

 rounded below, obliquely truncated above. Beak small, but 

 little elevated above the hinge-line ; umbonal ridge arcuate, 

 extending from the beak to the postero-ventral margin. Sur- 

 face marked by inconspicuous concentric lines of growth. 



Remarks. This species differs from 8. iowensis in its 

 much greater length. It resembles 8. gregarius H., from the 

 Chemung group in New York, but is a longer shell. In 

 fact 8. gregarius is somewhat intermediate in its characters 

 between this species and 8. iowensis. The specimen illus- 

 trated was attached to the same card in the University of 

 Michigan collection, with the types of Edmondia jejunus, 

 but it is entirely different from that species, not even being 

 generically allied to it. 



Cypricarbinia sulcifera (Win.). 



PI. III. f. 1 7. 



Shell small, subovate in outline, very oblique; length, 7 mm., 

 breadth, 4 mm. Hinge-line straight, shorter than the total 

 length of the shell ; anterior margin abruptly rounded ; ven- 

 tral margin nearly straight or sinuate in the middle; pos- 



