TABLE T. 



A. 



TRILOBITES AND rUCOIDAL IMPllESSIONS, FROM THE LOWEST PROTOZOIC SANTISTONES, F. I., 

 OF WISCONSIN AND MINNESOTA. 



Mcdal-rulcd on Steel from the Original Specimens. 



T:\\i. I. A, Fig. 1. Slab of gritstone, from the Miniskah, or third Trilobite-bed of F. 1, containing, along with other less per- 

 fect impressions, part of the cephalic shield of Oikelocephalus Minnesotensis. 

 The exquisite effect and truth of the medal-ruling process are beautifully exhibited in tlie maimer in which 

 it has brought out not only the fossils but the grain of the rock, in this specimen. 

 " Fig. 2. Fucoidal impressions in the layers under the Marine Mill Trilobite-grit, St. Croix River, Minnesota. 



Singularly enough, part of the impression bears a fantastic resemblance to a reclining human figure in 

 bas-relief. 



" Fig. 3. Cheek-plate and cephalic spine of Dikclocej)halus Minnesotensis {'.), found in the buff magnesio-calcareous 

 layers near the base of La Grange Mountain, at the head of Lake Pepin, Upper Mississippi. 



" Fig. 4. Part of the cheek-plate and cephalic spine of Dikelocepliabts Miniscaensis, near the confluence of the 

 Miniskah and Mississippi Rivers. 



" Fig. 5. Glabella of Dikeloecphalus Miniscaensis, near the mouth of the Miniskah River. 



" Fig. 6. Glabella of Dikelocephalus Minnesotensis, near the head of Lake Pepin, 



" Fig. 7. Cephalic spine and part of cheek-plate of Dikelocephalus Pepinensis (?), near the head of Lake Pepin. 

 " Fig. 8. Curious fishhook-shaped spine, which was attached to the posterior part of the glabella of Lonchocephalus 

 hamulus, projecting backwards in the median line of the body. From the third Trilobite-bed, near the 

 ' mouth of Miniskah River. 



" Fig. 9. Embedded portion of cephalic shield of Lonchocephalus Chippcivaensis, showing the spicula or small spine 



projecting backwards from the glabella in tlie median line. 

 " Fig. 10. Glabella of Crepicephalus (N. (j.), near Miniskah. 



" Fig. 11. Pygidium and caudal sjDine of an undetermined Trilobite ; near Mountain Island. 



" Fig. 12. Glabella, with spine attached, o£ Lonchocephalus liarnuhis (N. S.) ; from the Miniskah Trilobite-bed. 



Fig. 13. Pygidium of Dikelocephalus (?) lowensis, Mississippi, near Mountain Island. 

 " Fig. 14. Pygidium of Crepicephalus (?) Miniscaensis (N. S.), from the Miniskah grits. 



'■ Fig. 15. Pygidium of Lonchocephalus (?), with long, slender, divergent caudal spines. Near Mountain Island. 

 " Fig. IG. Pygidium and portions of Crepicephalus (?), and portions of cephalothorax of that genus; from the Minis- 

 kah Trilobite-grit. 



" Fig. 17. Glabella of Dikelocephalus Pepinensis (?) ; from the buft'beds near the head of Lake Pepin. 

 " Fig. IS. Glabella of Crepicephalus : near Miniskah, Mississippi River. 



