PAGE. 



Fig. 25. OKBICULOIDEA LAMELLOSA Hall (?) 364 



A dorsal valve, provisionally referred to this species. Hudson River group, 

 Spring Valley, Minn. Collection of C. Schuchert, 



Figs 26 to 2V. ScHizoTi'.ETA PELOPEA Billings 365 



26. A dorsal valve. 



27. A ventral valve, showing the small oval pedicle opening. Middle Galena lime- 



stone, Mantorville, Minn. Minnesota Geological Survey collection. 



28. Natural cast of the interior of the ventral valve, pa, posterior adductor scars. 



Hudson Kiver group at Spring Valley, Minn. University of Minnesota col- 

 lection. 



FigS. 29 to 31 . SCHl/OCKANIA FILOSA Hall 370 



29. A dorsal valve, showing the large posterior adductor scars. 



30. Profile outline of same , attached to a gastropod. Trenton limestone. Cannon 



Falls, Minn. Collection of W. H. Scofleld. 



31. A specimen in which the upper, or dorsal, valve has been removed, exposing the 



internal characters of the ventral valve. B, dorsal valve; r, ventral valve; y, 

 pedicle groove; I, walls of groove; x 2. (After Hall.) Hudson River group, 

 Covington, Ky. 



Figs. 32 and 33. CRANIA SETIGEBA Hall 372 



An upper, or dorsal, valve, showing the spiniferous surface of the species. 

 33. _ Profile view of the same specimen. (After Hall.) Trenton limestone at Mineral 

 Point, Wisconsin. 



Figs. 34 and 35. CRANIA GRANULOSA N. H. Winchell 373 



A dorsal and profile outline view of the type specimen. Trenton limestone at 

 Minneapolis, Minn. Minnesota Geological Survey collection. 



Figs. 36 and 37 . CRANIA TRENTONENSIS Hall 374 



Dorsal and profile views of the type specimen. (After Hall.) Trenton limestone, 

 Middleville, New York. 



Figs. 38 and 39. CRANIELLA (?) ULRICHI Hall 375 



38. A cast of the interior of the ventral valve, somewhat restored on the right side, 



showing the strong anterior and very obscure posterior adductor impressions, 

 and the marks of the vascular sinuses. 



39. The internal cast of a dorsal valve referred to this species, showing the muscular 



scars and the sigmoid vascular impressions. (After Hall.) Trenton shales, 

 Minneapolis, Minn. Collection of C. Schuchert. 



Fig. 40. PHOLIDOPS TRENTONENSIS, var. MINOR, n. var 376 



A dorsal valve (?), x 3. Trenton shales, St. Paul, Minn. Collection of C. 

 Schuchert. 



Fig. 41. LINGULA MODESTA Ulrich 344 



Ventral valve of a small specimen x 4, and outline of the. natural size. 



l'"ig. 42. LINGULA CLATIIRATA, n. sp 345 



Ventral valve of an average sized specimen x 3i, and outline of natural size. 



