Figs. 43 to 45. 
Figs. 46 to 50. 
46, 47 and 48. 
49. 
50. 
Figs. 51 to 58. 
51, 52 and 53. 
54 and 55. 
56 and 57. 
58. 
Figs. 59 and 60. 
59. 
60. 
PAGE. 
OF (OB) anos VE CHOI IN MEIGS Socohta“codagans tose n500 oseenono sn odoar 
Dorsal, ventral and profile views of a very characteristic specimen of this variety. 
Galena shales, near Cannon Falls, Minn. Collection of C. Schuchert. 
ORTHIS (/DINOR THIS) (SUBQUAD RATA pal) Sis velar ate watt inters) ste eiclcisiels o\eiele sielelele)elelels 
Dorsal, ventral and profile views respectively of an entire specimen. Minnesota 
Geological Survey collection. 
An interior view of the ventral valve of a very old specimen in which the anterior 
margin is much thickened and reflexed. The vascular sinuses are abnormally 
developed, due to old age. Hudson River group, Spring Valley, Minn. 
Interior of a dorsal valve. (After Meek, Ohio Pal., vol. i.) 
OETHIS | (DINORTHIS)) PROAVITAMW A ANG Staves atiatsral ote tte) sereteneta a Miele|elelais elata\clets|«)ele/e\e/= 
Dorsal, ventral and profile views of an entire specimen. Collection of the Min- 
nesota Geological Survey. 
Dorsal and profile views of a large specimen. Hudson River group, Wilmington, 
Tlinois. 
Interior and profile views of a thick ventral valve. Hudson River group, Spring 
Valley, Minn. 
Interior of a dorsal valve. Hudson River group, Spring Valley, Minn. Collec- 
tion of C. Schuchert. 
RAFINESQUINA ALTERNATA, var. LOXORHYTIS MeeKk......5....+----+--20---eeee 
Perpendicular view of the hinge and muscular impressions of the specimen illus- 
trated on plate XXXII, fig. 37. 
Profile view of the same specimen. 
428 
431 
407 
