Cryptozoon Minnesotense at Northfield — Chaney. 281 



and came upon them again. As the class had been considering 

 the smaller cryptozoa not long before, Messrs. Higbee and Win- 

 gate at once suspected that these might be such fossils on a gigan- 

 tic scale. Upon their report I at once began examination, care- 

 fully measuring the formations and noting peculiarities of arrange- 

 ment and taking photographs. The results of that examination 

 are now presented. 



At Northfield the Shakopee outcrops on both sides of the Can- 

 non river, forming the immediate banks, while the bluffs at a 

 greater distance are of the St. Peter sandstone. Wherever seen, 

 the Shakopee limestone presents many peculiarities. It is full of 

 flinty layers of unusual structure and its strata are exceeding ir- 

 regular in composition and arrangement. A quarter of a mile be- 

 low the town begins the ledge before spoken of, and it extends 

 along the railway for h alf a mile or more. Along the face of the ledge 

 at a height of from fifteen to twenty feet above the river is a very 

 distinctly marked shelf which projects in some place two feet. 

 Above this shelf are to be found the dome shaped masses which 

 are now to be considered. As may be seen from Fig. 5, they pre- 

 sent upon the 



face of the \ -'- — r"^ r~^-V- 1 

 ledge the ap- 

 pearance of 

 concentric 

 layers, quite 

 fine and close 

 near the lower 

 central part, 

 becoming 



tniCker and Fig. 5, showing structural features in the Shakopee limestone 



coarser as we ^* Northfield. 



proceed toward the outside. The inner layers curve somewhat 

 sharply and seem to rest upon their edges on the shelf before 

 mentioned. The outer layers change their direction and be- 

 come apparently continuous with the adjacent horizontal layers. 

 Occasionally two domes abut against each other. The line of 

 division is then clearly marked, as a rule, and takes on two 

 forms. One dome may be complete, its layers extending down 

 to the general level upon which all seem to rest. The adjacent 

 dome rests with the ends of its layers upon the sloping side of the 



