726 



SCIENCE 



[N. S. Vol. XXVII. No. 697 



tive rapidity, producing before its close the 

 remarkable series of northward splitting 

 beaches which are associated with Lake 

 Algonquin. 



Following the discussion of the beaches 

 of Lake Algonquin, the Nipissing Great 

 Lakes were described with their outlet east- 

 ward through Lake Nipissing to the Ottawa 

 River. Continuing uplift raised this out- 

 let and turned the discharge of the upper 

 lakes back once more to Port Huron, where 

 it has remained to the present time. 



The character of the causes of the 

 deformation of the old water planes was 

 discussed very briefly (a) with reference 

 to the effects produced on the water planes 

 within the Great Lake area, (6) in the 

 light of Pleistocene deformations affecting 

 wider areas, and (c) in the light of the . 

 leading theories concerning the conditions 

 of matter in the interior of the earth. 



The Mississippian Section in Illinois: 



Stuaet Wellek, Chicago, 111. 



No detailed studies of the Mississippian 

 rocks of Illinois have been reported for 

 over a generation. In the meantime much 

 progress has been made in the study of 

 the equivalent formations in neighboring 

 states, and much information regarding 

 them has accumulated. In view of these 

 conditions it has seemed desirable to con- 

 duct a series of investigations upon these 

 formations in Illinois where the typical sec- 

 tions occur, using the more modem methods 

 of stratigraphy and paleontology. The 

 present paper is a report of progress of 

 these studies which have been carried on 

 during the last two years. 



Devonic Elements in the Late Siluric 

 Fauna of Southern Michigan:^ A. W. 

 Grabau, New York, and W. H. Sherzer, 

 Tpsilanti, Mich. (Read by W. H. 

 Sherzer. ) 



' By permission of Dr. A. C. Lane, state geolo- 

 gist of Michigan. 



In southern Michigan the Monroe forma- 

 tion forms the upper part of the Siluric. 

 In the upper part of this formation and 

 about 200 feet below its summit is an in- 

 tercalated coral-reef limestone 40 to 50 

 feet thick, made up of Siluric and Devonic 

 stromatoporoids and corals, and containing, 

 besides, a number of other fossils related to 

 species elsewhere in this country known 

 only from the lower Middle Devonic. The 

 highest beds of the region contain an upper 

 Siluric fauna of European affinity. The 

 bearing of these facts on the paleogeog- 

 raphy of the Upper Siluric and on faunal 

 development and migration was discussed. 



Notes on the Traverse Group of Michigan:* 

 A. W. Grabau, New York City. (Read 

 by W. H. Sherzer, Ypsilanti, Mich.) 

 During the progress of the study of the 

 stratigraphy and faunas of the Traverse 

 Group of northern lower Michigan— a 

 number of distinct faunal divisions have 

 appeared. The subdivisions of the group 

 and the migrations of the successive faunas- 

 were considered, and the progressive evolu- 

 tion of some of the characteristic species 

 was traced. 



The Evolution and Distribution of the 

 Plesiosaurs: S. W. Williston, Chicago, 

 111. 



The known range of the Plesiosauria of 

 North America is from the Upper Jura 

 (Baptanodon beds) to the middle or upper 

 part of the Fort Pierre Cretaceous. A 

 comparison of nearly all the known ma- 

 terial from North America with much of 

 that from Europe gives assurance that no 

 known genus is certainly common to the 

 two continents. The genus Plesiosaurus,. 

 especially, the most generalized of the 

 known plesiosaurs, is certainly not repre- 

 sented by any known species in America^ 



* By permission of Dr. A. C. Lane, state geolo- 

 gist of Michigan. 



