T.MWA'] T. 



TRILOBITKS OF THE I,OWEST KANDSTOXES OF WISCONSIN ANT) ]MINNESOTA. 



Medal-ruk'd on Steel, from ilie Original Specimens. 



This mode of engraving, from the actual spccinieiLS, Iiy wliicli a perfect fac simile is obtained, has been applied, I 

 believe, for the first time, in the execution of eight of the plates of organic remains accompanying this work. The result, 

 for a first experiment, has been eminently successful ; at least applied to subjects not having too great reliefer convexity, 

 as will be observed by inspection of this and tlie other seven plates engraved by this process. 



Until the discovery of the Trilobites represented in this and the succeeding plate, collected during this Survey, no 

 Crustacean remains had been found in any rocks older than the Trenton, Black River, and Chazy Limestones of the State 

 of New York. 



Tab. I., Fig. 1. Dikeloccphahis Minncsotemis. (N. S.) From the fifth Trilobite-bed of F. 1, on the banks of the St. Croix, at 

 Stillwater, Minnesota. Restored outline, in dim contour. 

 " Fig. 2. Dikchceplialus Minncsoicmis. Pygidium of a smaller individual, showing the short caudal appendages. 



Fig. 3. Dikelocephalus Miniscaensis. (N. S.) From the third Trilobite-bed of F. 1. 

 " " a. Part of cephalic shield. 

 " " b. Pygidium. 



" Fig. 4. DUalocephahis? loiccnsis. (N. S.) From the first or lowest Trilobite-bed, 400 to -1.50 feet beneath the base 



of the Lower Magnesian Limestone. 

 " Fig. 5. Dilclocephalus granvhsiis Pygidium, from the third, or Miniskah Trilobite-bed. 



" Fig. C. Loiichorcphalus Cliippctcaensis. (N. S.) Part of cephalothorax and caudal shield, from the fourth, or Marine 



* Mill Trilobite-grit, atout 170 feet below the top of F. 1. 



" Fig. 7. Dikdocejilialm granulosus. (N. S.) Part of cephalothorax, from the third, or Miniskah Trilobite-bed. 

 '■ Fig. 8. C'rcpiccphabis:^ Pygidium, from the Miniskah Trilobite-grit. 



Fig. 9. Dikelocephalus Pepincnsis. (N. S.) From the huff magnesian layers in F. 1, near the base of La Grange 

 Mountain, at the head of Lake Pepin. 

 " " a. Part of cephalothorax. 

 " " b. Pygidium. 



" Fig. 10. DUcclocephalus (Jtlinncsolcnsis?) From the bufl" magnesian layers with the last. 

 " Fig. 11. Menocephalus Minnesoiensis. Glabella; froin the third Trilobite-bed, Miniskah. 

 " Fig. 12. Dikelocephalus Miniscaensis? From the Miniskah Trilobite-bed. 



" Fig. 13. Crepicephalics? Wisconsensis. (N. S.) Part of cephalothorax, and a portion of the cephalic shield of D. 

 granulosus f 



" Fig. 14. Loiichoeeplirilii'i Chiiipoi-noifiis ' fN. S ) From the fourth Trilobite-bcd, on flic Menomonie River. 



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