276 Revieics — American Geological Surveys, Michigan. 



mentary origin, thougli often presenting combinations suggestive of 

 an igneous character. The following is their order, in descending 

 scale : — 1. Quartzite, 2. Hematitic and Magnetic Ores, 3. Ferru- 

 ginous Quartzite, 4. Diorite, 5. Ferruginous Quartzite, 6. Diorite, 7. 

 Ferruginous Quartzite, 8. Diorite, 9. Ferruginous Quartzite, 10. 

 Diorite, 11. Talcose schist, 12. Quartzite, 13. Laurentian. The 

 Copper region, under the superintendence of Professor Pumpelly, 

 is being mapped upon the scale of 300 feet to the inch. The field- 

 work has led to the accumulation of numerous details respecting 

 the distribution of the several formations, which cannot be presented 

 in a report of progress, but they have necessitated many improve- 

 ments upon the Geological Map, 



Closely connected with the results of the field-work is an elaborate 

 paper by Professor Winchell upon the Marshall Group, in the Pro- 

 ceedings of the American Philosophical Society. The Michigan 

 Reports present an array of many new local names. This has been 

 necessitated by the isolated position of the Carboniferous and De- 

 vonian Kocks of the Lower Peninsula. The Marshall Group is 

 proved to lie at the base of the Carboniferous System, and to be the 

 equivalent of part of the Waverley series of Ohio, the Catskill group 

 in New York, the Goniatite Limestone of Indiana, the Kinderhook 

 group of Illinois, the Yellow Sandstones (Hall) of Iowa, the Chonteau 

 Limestone, vermicular Sandstone and lithographic Limestone of 

 Missouri, and the Silico-bituminous shales at the base of the Sili- 

 ceous group of Tennessee. This is a novel conclusion in American 

 Geology. Most geologists have followed the lead of Professor James 

 Hall, who regarded them generally as the equivalents of the Chemung 

 and Portage groups, at the summit of the Devonian, while the Cats- 

 kill Eed Sandstone has headed the column of the New York system 

 for the past thirty years as beneath the Carboniferous. This con- 

 clusion is adopted, at least for the State of Ohio, by Dr. Newberry 

 and others. The theory is based both upon lithological and palgeon- 

 tological grounds. In this ' ' Marshall group ' ' Professor Winchell finds 

 that there have been collected 416 species of fossils, viz., nine plants, 

 thirteen Polypi, 27 Crinoids, one Fenestella, 124 Brachiopods, 116 

 Lamellibranchiates, 13 Belleroplion, four Forcellia, 48 Gasteropods, 

 46 Cephalopods, nine Trilobites, one Ostracod, four Fishes, and one 

 Pleurodictya. These identified species have been collected in eleven 

 detached districts or States, which have yielded severally the follow- 

 ing numbers: — North Michigan, 23; South Michigan, 93; Ohio, 139; 

 Indiana, 45 ; Illinois, 27 ; Iowa, 160 ; Missouri, 77 ; Kentucky, 2 ; 

 Tennessee, 13 ; New York, 9 ; Pennsylvania, 9 ; total, 597. Great 

 additions have since been made to this list in Ohio. 



The Waterlime division of the Lower Helderberg formation has 

 now been found in Michigan. It contains the Eurypterus remipes 

 (De Kay). An apparentl}'^ new assemblage of Hamilton and Cornifer- 

 ous Limestone species is found in the i-ocks of the Lower Peninsula, 

 and has received the name of the " Grand Traverse group." The 

 "Huron group" contains a peculiar assemblage of fossils, and the 

 term may be a better one than its New York equivalent, the Genesee 

 and Portage groups. 



