128 Trans. Acad, JSci. of St. Louis. 



types of P. nodocostatus (W. & W.). U. of M. Coll., No. 1390 and U. of C. 

 Coll., No. 5935. — 3, Aviculopecten tenuicostus Win. One of the type speci- 

 mens. U. of M. Coll., No. 1392. — 4, Aviculopecten caroli Win. One of the 

 type specimens. U. of M. Coll., No. 1393. — 5, Pernopecten ? sp. This 

 specimen may belong to Posidomya ? ambigua Win. U. of C. Coll., No. 

 5936.-6-7, Pteronites whitei (Win.). Two of the type specimens. U. of 

 M. Coll., No. 1384. — 8-9, Leiopteria spinulata (Win.). A. left and aright 

 Talve, two of the type specimens. U. of M. Coll., No. 1382-1383. — 10, Avi- 

 cula strigosa (^White). One of the type specimens. U. of M. Coll., No. 

 1387. — 11, Mytilarca occidentalis (W. & W.) Left view of the type speci- 

 men. U. of M. Coll., No. 1400 — 12, Mytilarca fibristriata (W. & W.). 

 Left view of the type specimen. U. of M. Coll., No. 1399.-13-14, Gonio- 

 phora jennae (Win.). Two of the type specimens. U. of M. Coll., No. 

 1428. — 15, Macrodon cochlearis Win. One of the type specimens. U. of 

 M. Coll., No. 1422. — 16, Macrodon modesta (Win.). The type specimen 

 U. of M. Coll., No. 1420. — 17, Cypricardinia sulcifera (Win.). One of the 

 type specimens. U. of M. Coll., No. 1415. — 18, Cardiopsis megambonata 

 Win. View of a left valve, not the type specimen. U. of M. Coll., No. 1429. 



Plate IV. — 1-2, Edmondia burlingtonensis W. & W. Two of the type 

 specimens. U. of M. Coll. No. 1405. — S, Edmondia aequimarginalis Win. 

 View of a left valve, not the type specimen. U. of M. Coll., No. 1408. — 4, 

 Edmondia nitida Win. The type specimen. U. of M. Coll., No. 1406. — 5, 

 Edmondia jejunus (Win.). One of the type specimens. U. of M. Coll., No. 

 1416 (in part). — 6, Olossites elliptica (Win.). The type specimen. U. of M. 

 Coll., No. 1411. — 7, iSphenotus iowensis (Win.). The type specimen. U of 

 M. Coll., No. 1414 (in part). — 8, Sphenotus bicostatus n. sp. The type 

 specimen. U. of M. Coll., No. 1414 (in part). — 9, Sphenotus rigidus (W. 

 & W.). One of the type specimens. U. of M. Coll., No. 1417. — W, Spheno- 

 tus bicarinatus (Win.). One of the type specimens. U. of M. Coll., No. 

 1410. — 11, Glossites ? burlingtonensis n. sp. The type specimen. U. of M. 

 Coll., No. 1412 (in part). — 12, Spathella ventricosa (W. & W.). One of the 

 type specimens. U. of M. Coll., No. 1402. — 13-14, Schizodus iowensis n. sp. 

 The type specimens, a right ami a left valve. U. of M. Coll., No. 1419 (in 

 part). — 15, Schizodus burlingtonensis n. sp. The type specimen. U. of M. 

 Coll., No. 1416 (in part). — 16, Grammysia amygdalinus (Win.). The type 

 specimen. U. of M. Coll., No. 1412. — 17, Edmondia quadrata (W. &W.). 

 One of the type specimens. U. of M. Coll., 1430. — 18-19, Posidonomya 7 

 ambigua Win. Two of the type specimens. U. of M. Coll., No. 1430. — 20, 

 Promacrus cuneatus H. View of the type specimen (after Hall). — 21, Gram- 

 mysia plena B.. View of a left valve (after Hall). 



Plate V. — 1-2, Porcellia crassinoda W. & W. Lateral and dorsal views of 

 the type specimen. U. of M. Coll., No. 1441. — 3, Porcellia obliquinoda 

 White. Lateral view of the type specimen. U. of M. Coll., No. 1442. — 4-5, 

 Strophostylusbivolve (W. & W.). — Two views of one of the type specimens. 

 U. of M. Coll., No. 1444. 



Plate VI.— 1-2, Sphaerodoma pinguis (Win.) Two views of the type 

 specimen. U. of M. Coll., No. 1461. — 3-4, Naticopsis depressa Win. Two 

 views of one of the type specimens. U. of M. Coll., No. 1464. — 5, JBucan- 

 opis deflectus n. sp. A dorsal view of the type specimen. U. of M. Coll., No. 

 1437 (in part). —6, Pa«eZZos«m??i scnjpJi/erMS (White). Dorsal view of the 



