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In conclusion I wish to protest against the restoration Huene has 

 made of my figure of the pelvis of Eubrachiosaurus Will. (p. 49). The 

 outlines as I gave them are essentially correct, and the bones do not 

 belong on the right side. As to the distinction of the genus from 

 Placerias Lucas, I am, however, not so sure. 



S. W. WlLLISTON 



The Monroe Formation of Southern Michigan and Adjoining Regions. 

 By A. W. Grabatj and W. H. Sherzer. [Michigan Geo- 

 logical and Biological Survey. Publication 2. Geological 

 Series 1.] 

 This report describes a series of Paleozoic beds and their faunas which 

 have their greatest development in southeastern Michigan and the 

 adjacent portions of Ontario and Ohio. In the past these strata, which 

 constitute the Monroe formation, have been much misunderstood, and 

 their importance in the Paleozoic section of the region has been greatly 

 underestimated. The maximum thickness of the formation is about 

 1,200 feet. 



The Monroe as a whole is divided into two series of dolomitic beds, 

 the Lower and Upper Monroe, separated by the Sylvania sandstones, 

 a bed of exceptionally pure, white, and almost incoherent sand in its 

 more typical development, but merging into arenaceous dolomites in 

 its less typical expression. The maximum thickness of the Sylvania 

 is 300 feet, and the peculiar nature of the formation is explained on the 

 hypothesis that it is an aeolian deposit laid down under essentially desert 

 conditions, the original source of the material being the exposures of the 

 Saint Peter sandstone to the northwest in Wisconsin. 



The Monroe faunas are described in detail and are illustrated by 

 twenty-five plates; 126 species in all are defined, many of them new 

 forms, and seven new genera are proposed. The faunas of the two 

 divisions of the Monroe are shown to be essentially different, there being 

 almost no species in common. The Lower Monroe faunas are all late 

 Silurian in aspect, being more or less closely related to the Manilus and 

 Rondout formations of eastern New York. In the lower divisions of 

 the Upper Monroe a conspicuous coral element appears which was 

 entirely lacking in the. Lower Monroe faunas, and among these corals 

 are many strikingly Devonian forms; among the brachiopods are found 

 both Devonian and Silurian types; the pelecypods are Devonian while 

 the gastropods and cephalopods are essentially Silurian in aspect. 



