ABSTRACTS OF PAPERS 121 



little significance; for, where boulders are abundant, boulder bars may form 

 in vigorous streams adjacent at any time. 



Considering these points alone, we must claim that it has not been proven 

 that the valley of the Missouri is preglacial. 



Presented by title in the absence of the author. 



FORMER COURSES OF THE ANDROSCOGGIN RIVER 

 BY IRVING B. CROSBY 1 



(Abstract) 



The present course of the Androscoggin is largely preglacial in origin, being 

 composed of parts of three preglacial drainage systems. The upper part of 

 the Androscoggin drainage basin was formerly tributary to the Connecticut 

 River. The middle part drained through the basin now occupied by Sebago 

 Lake into the ocean south of Portland, and the drainage of the lower part was 

 somewhat as at present. The disarrangement of drainage lines in the middle 

 and lower parts was due to heavy deposits of glacial drift. The upper part 

 was captured from the Connecticut system by preglacial piracy. 



Presented by title in the absence of the author. 



PENEPLAINS AND THE GEOGRAPHIC CYCLE 

 BY WILLIAM MORRIS DAVIS 



The full paper is to be published in this volume of the Bulletin. 



Presented in abstract extemporaneously. 



Discussed by D. W. Johnson, Oscar E. Meinzer, and H. F. Cleland. 



Discussion 



Professor Johnson : It is desirable to distinguish between the uplifted de- 

 posit of sediments commonly called a coastal plain and a level surface of ero- 

 sion bordering the coast, which is sometimes also called a coastal plain. By 

 employing the spelling plane for planes of erosion, the desired distinction will 

 at least be apparent on the printed page and the confusion evident in some 

 reports be avoided. A peneplane is almost a plane surface of erosion, a region 

 planed down by the agents of erosion. The spelling ane instead of ain has 

 proved useful to the speaker, while at the same time being closer to the Latin 

 root and less open to criticism as a hybrid. 



RETROGRADING OF OFFSHORE BARS 

 BY DOUGLAS W. JOHNSON 



(Abstract) 



In the normal development of a shoreline of emergence there occurs a stage 

 during which the offshore bar retreats landward under the continued attack 

 of the waves. Inasmuch as this process of retrograding involves the super- 



1 Introduced by W. O. Crosby. 



