PAGE. 



Tigs. 29 and 30 HELCIONOPSIS STKIATA Ulrich 827 



Profile and dorsal views of a gutta percha cast of a natural mold of the exterior 

 in the base of a bryozoan. Richmond group, Marion county, Kentucky. 



Figs. 31 and 32 SCENELLA RADIALIS U. and S 841 



Two views of the type of this species. The specimen is a cast of the interior. 

 Trenton group, St. Paul, Minnesota. Geological and Natural History Survey 

 of Minnesota, Museum Register No. 5535. 



Figs. 33 and 34 SCENELLA BBLOITENSIS U. and S 839 



Two views of an internal cast preserving muscular imprints. Stones River group, 

 Beloit, Wisconsin. Collection of the University of Wisconsin. 



Fig. 35 SCENELLA SUFEKBA Billings sp 838 



Profile view of a specimen of the average size and proportions. Stones River 

 group, Cannon Falls, Minnesota. 



Figs. 36 and 37 SCENELLA AFFINIS U. and S 840 



Two views of a nearly perfect example of the typical form of this species. Be- 

 sides the transverse wrinkles shown in the figures, the specimen preserves 

 obscure remains of very fine radiating and concentric lines. Black River 

 group, Goodhue county, Minnesota. 



Figs. 38 to 41 SCENELLA COMPKESSA U. and S 840 



38 to 4n Three views of a cast of the interior, the compressed form slightly exaggerated by 

 pressure. The second outline shown on two of the figures is intended to show 

 the probable original dimensions of the specimen. 



41 Portion of external surface, obtained from a gutta percha impression of a natural 

 mold, x3. 



Figs. 42 to 44 STENOTHECA UNOUIFORMIS Ulrich 843 



Profile and dorsal views of an average example, and part of its surface, *3. Tren- 

 ton group, Mercer county, Kentucky. 



Figs. 45 to 48 PAL^EACM^EA HUMILIS U. and S 837 



45 and 46 Two views of a small but well preserved example. Ctenodonta bed of the Black 

 River group, Goodhue county, Minnesota. 



47 and 48 Similar views of a cast of the interior from the Vanuxemia bed of the Stones 

 River group at Minneapolis. Geological and Natural History Survey of Minne- 

 sota, Museum Register No. 5104. 



Figs. 49 to 54 PLATYCEKAS (?) WISCONSINENSE U. and S 1068 



Two views each of three casts of the interior showing the variable nature of this 

 shell. Stones River group, Beloit, Wisconsin. Collections of the University of 

 Wisconsin, and of E. O. Ulrich. 



Figs. 55 and 56 PLATYCERAS (?) DEPKESSUM U. and S 



Two views of the type of this species. It preserves the shell and was collected 

 from the Ctenodonta bed of the Black River group, near Cannon Falls, Minne- 

 sota. 



1069 



