Apeil 16, 1909] 



SCIENCE 



635 



section lie far beneath the limestones. The areal 

 distribution, contacts and structural lines point to 

 a strong overthrust fault of wide extent. 



This paper was discussed by Professor J. Bar- 

 rel!. 



After this was read: 

 Recurrence of the Tropidoleptus Fauna and the 



Geographic Range of Certain Species in the 



Chemung of Maryland: Chabuss K. Swaktz, 



Baltimore, Md. 



The recurrence of Tropidoleptus and associated 

 species of Hamilton type above the base of the 

 Chemung of Maryland was noted. Certain diag- 

 nostic species of the Chemung, particularly those 

 of the genera Douvillina and Dalmanella, appear 

 to be of rare occurrence east of the Allegheny 

 Front. The significance of this fact was discussed. 



Discussion of the foregoing paper was partici- 

 pated in by Professors H. S. Williams, H. P. 

 Cleland, Charles Schuchert, C. K. Swartz, J. M. 

 Clarke, Stuart Weller, E. R. Cumings and C. S. 

 Prosser. 



Then was read: 

 The Geological Distribution of the Mesozoic and 



Cenozoio Echinodermata of the United States : 



Wm. BuiioCK Clabk and M. W. Twitchell, 



Baltimore, Md., and Columbia, S. C. 



The authors presented the results of an investi- 

 gation of the Mesozoic and Cenozoic echinoder- 

 mata of the United States, particularly in refer- 

 ence to the geological distribution of the forms 

 studied. Representatives of the eohinodermata 

 are found at most horizons, but are numerous and 

 significant in the Cenozoic and Tertiary rocks, 

 where they at times become important forms for 

 the determination of geologic horizons. The 

 Upper Cretaceous formations both of the Atlantic 

 and Gulf states have afforded a large number of 

 important species. 



The paper was discussed by Dr. J. M. Clarke 

 and Professor W. B. Clark. 



The next paper read was: 

 On the Age of the GaspS Sandstone: Heney S. 



Williams, Ithaca, N. Y. 



A review of the evidences upon which has been 

 based the opinion that the marine fauna at the 

 base of the Gaspfi sandstone is of the Hamiltonian 

 epoch, and a presentation of the evidence for the 

 view that these marine beds, as well as those of 

 Pictou iron ore beds of Nova Scotia, Moose River 

 sandstone of Maine and the upper beds of the 

 St. Helen's Island conglomerate and of C5te St. 

 ir'aul, are not of later age than the Oriskany beds 

 immediately underlying the Onondaga limestone 



of North Cayuga, Ontario or Schoharie grit of 

 eastern New York, at which epoch it is inferred 

 marine connection with the Atlantic basin was 

 cut off. 



The Owl's Head and Chaudifere River beds were 

 explained by supposing the opening of a channel 

 westward, connecting with Indiana basin and 

 southwest at beginning of the succeeding Onon- 

 daga epoch. 



The paper was discussed by Professors J. M. 

 Clarke, Charles Schuchert, H. S. Williams and 

 A. W. Grabau. 



The section adjourned at 12:30 p.m. and met 

 again at 2 : 15 P.M. with Professor W. B. Clark in 

 the chair. 



The following two papers were read by title: 



The Aftonian Sands and Gravels in Western 



Iowa: BoHUMiL Shimek, Iowa City, Iowa. 

 An Aftonian Mammalian Fauna: Samuel Calvin, 



Iowa City, Iowa. 



Then was presented: 

 The Brachiopoda of the Richmond Group: August 



F. FoEESTE, Dayton, Ohio. 



In the area dominated by the Cincinnati geanti- 

 cline there have been several invasions of the 

 brachiopoda considered most typical of the Rich- 

 mond group. The first of these occurred near the 

 middle of the deposition of the Arnheim bed. The 

 Richmond group .of the Mississippi Valley, as far 

 as may be determined from a study of the brachio- 

 poda, finds nearer representatives in the upper or 

 Blanchester division of the Wayneaville bed and 

 in the Liberty bed, than in the Arnheim, lower 

 Waynesville or Whitewater beds. A study of the 

 distribution of the brachiopoda in Ohio, Indiana 

 and Kentucky suggests that the centers of distri- 

 bution lay more frequently toward the northeast 

 than toward the northwest or west of the present 

 areas of exposure. To account for this it is 

 imagined that the Richmond group of the Ohio 

 Valley was connected with that of the Mississippi 

 Valley by way of northern Indiana and Illinois. 

 Possibly, if the areas now covered by overlying 

 formations could be exposed, the Richmond 

 brachiopoda would be found to be absent in 

 southern Indiana and Illinois and in western Ken- 

 tucky, west of the present areas of exposure of 

 these fossils in the region of the Cincinnati gean- 

 ticline. Lithological conditions within the areas 

 dominated by this geanticline favor this view. 



Professor E. R. Cumings discussed this paper. 



After this, the following paper was read: 



The Trap Sheets of the Lake Nipigon Basin: Al- 

 FEED W. G. Wilson, Montreal, Canada. 



