April-May 1920 Vol. XXVIlI, No. 



The Journal of Geolog 



Edited By 

 thomas c. chamberlin and rollin d. salisbury 



With the Active Collaboration of 



STUART WELLER ALBERT JOHANNSEN 



Invertebrate Paleontology Petrology 



ROLLIN T. CHAMBERLIN 



Dynamic Geology 



The Journal of Geology is published by the University of Chicago at the University of Chicagi 

 Press, 5750 Ellis Avenue, Chicago, Illinois, semi-quarterly, on or about the following dates: February gi 

 March 15, May i, June 15, August i, September 15, November i, December 15, HThe subscription 

 price is $4.00 per year; the price of single copies is 65 cents. Orders for service of less than a half-? 

 year will be charged at the single-copy rate. If Postage is prepaid by the publishers on* all orders fror 

 the United States, Mexico, Cuba, Porto Rico, Panama Canal Zone, Republic of Panama, Hawaiiaifl 

 Islands, Philippine Islands, Guam, Samoan Islands, Shanghai. H Postage is charged extra as followsi 

 For Canada, 30 cents on annual subscriptions (total $4-3o), on singlfe copies 4 cents (total 69 cents)j 

 for all other countries in the Postal Union, 53 cents on annual subscriptions (total $4 53), on singly 

 copies 11 cents (total 76 cents). H Patrons are requested to make all remittances payable to The Uni^^ 

 versity of Chicago Press in postal or express money orders or bank drafts. 



The following are authorized to quote the prices indicated: " f 



For the British Empire: The Cambridge University Press, Fetter Lane, London, E.C. 4. Yearlyr 



subscriptions, including postage, 215. each;- single copies, including postage, 35. 6d. each. -.i 



For Japan and Korea: The MaruzeiwKabushiki-Kaisha, 11 to 16 Nihonbashi Tori Sanchome, 



Tokyo, Japan. Yearly subscriptions, including postage. Yen 9.00 each; single copies, including 



postage. Yen i . 50 each. ^ 



For China: The Mission Book Company, 13 North Szechuen Road, Shanghai. Yearly su||[ 



scriptions $4.00; single copies 65 cents, or their equivalents in Chinese money. Postage extra, if;l 



mailed direct outside of Shanghai, on yearly subscriptions 53 cents, on single copies 11 cents. | 



Claims for missing numbers should be made within the month following the regular month of publi|i 

 cation. The publishers expect to supply missing numbers free only when losses have been sustained in*; 

 transit, and when the reserve stock will permit. 



Business correspondence should be addressed to The University of Chicago Press, Chicago, 111. 



Communications for the editors and manuscripts should be addressed to the Editors of Thi 

 Journal of Geology, the University of Chicago, Chicago, 111. 



Contributors are requested to write scientific and proper names with particular care and in citatioij 

 to follow the form shown in the pages of the Journal. 



Separates, if desired, must be ordered in advance of publication. Separates of leading articles will 

 printed as ordered, of which 50 (without covers) will be furnished gratis, the actual cost of the remainder 

 (and covers, if desired) to be paid for by the author. The actual cost may vary, and will depend upoi^ 

 the amount of work in remaking the pages into forms, presswork, paper, binding, etc. Separates con-* 

 taining half-tones may be expected to cost somewhat more, the mcrease dependmg upon the number 

 of cuts and the amount of work required upon them. 



Entered aa second-class matter, March ao, 1893, at the Post-office at Chicago, 111., under the Act of March 3, 1870. 

 Acceptance for mailing at special rate of postage provided for in Section 1103, Act of October 3, 1917. authorized on 

 Tuly 15, 1018. 



._,J 



