REVIEWS — THE GEOLOGICAL SURVEY OF MICHIGAN. 73 



referred respectively to the genus Astylospongia of Ferdinand Rcemer, 

 and to a new genus named Eospongia by the author. These forms 

 are the more interesting, since undoubted examples of fossil sponges 



; do not appear to have been previously recognized in the Palaeozoic 

 deposits of Canada. Another interesting form, described in this 



.memoir, is a species of Ampyz, of which some fragmentary examples 

 have been discovered in the Chazy limestone of St. Dominique, in 

 the County of Yamaska, and also in the same formation at High gate 

 Springs in Vermont. E. J. 0. 



First Biennial Report of the Progress of the Geological Survey of 

 Michigan, embracing Observations on the Geology, Zoology, and 

 Botany of the Lower Peninsula. Published by Authority : Lan- 

 sing, 1861. 



iThis very creditable Report forms an octavo volume of four hun- 

 idred pages. Its contents emanate almost wholly from the State 

 ■ Geologist, Professor A. Winchell of Ann Arbor ; but a subordinate 

 tJReport.on the Zoology of the district embraced within the explora- 

 tion, is furnished by M, Miles ; and an account of the Botany of 

 the region is also contributed by N. H. Winchell. As the northern 

 '.portion of Michigan has been explored and reported upon by several 

 trustworthy geologists, amongst whom we may mention more es- 

 pecially Messrs. Whitney and Foster, and also the late Dr. Houghton 

 (drowned during the prosecution of the survey off Eagle River, 

 Lake Superior), the attention of Professor Winchell has been directed 

 in this instance to the more southern districts of the peninsula. In 

 his present Report, after a systematic and very able review of the 

 general geology of Michigan, including the connection of its various 

 formations with those of surrounding districts, a detailed analysis of 

 the salt wells, iron ores, coal, and other economic products of the 

 .. State, is entered into. Some useful tables of altitudes are also given. 

 The central portion of the peninsula of Michigan is occupied by 

 Carboniferous rocks, around which the older strata successively crop 

 out, presenting the basin-shaped form of arrangement so common in 

 Carboniferous districts generally. In addition to several exposures of 

 granitic rock (probably of Azoic age), together with the trappean 

 formations of Lake Superior, the following series of strata occur within 



