" Page. 
Figs. 46 and 47. O. (D.) sub^quata var. circularis N. H. Winchell 452 
Two views of the type specimen of Ch-this circularis Winchell, a brachial and 
profile. Trenton shales, Oxford Mills, Goodhue countj', Minn. Minnesota 
Geological Survey collection. 
Figs. 48 to 50. Orthis (Dalmanella) amcena N. H. Winchell 453 
Dorsal, profile and cardinal views of the type specimen. ? Galena limestone, 
Spring V^alley, Minn. Minnesota Geological Survey collection. 
Figs. 51 to 54. Platystrophia biforata Schlotheim, sp 455 
51 and 52. Ventral and cardinal views of a large specimen. 
53 and 54. Dorsal and profile views- of a specimen of the ordinary size. Galena shales, 
Goodhue county, Minn. Collections of W. H. Scofleld and C. Schuchert. 
Figs. 55 and 56. Platystrophia biforata var. crassa James 458 
Ventral and profile views of a nearly globose specimen. Hudson River group, 
Spring Valley, Minn. Collection of C. Schuchert. 
