502 I. 0. Russell — Glacial Records in the Newark /System. 



Fourth. The effect of a glacial period on animal and plant 

 life has received much attention, but what records of the pres- 

 ence of glaciers at any special time might be expected in con- 

 temporaneous fossils, is still indefinite. A glacial period is 

 usually considered as a cold period (the presence of local gla- 

 ciers in mountainous regions, however, does not imply an 

 Arctic climate). If a cold period followed a warm period, it 

 is to be expected that migrations of fauna and flora would fol- 

 low. Alternations of warm and cold periods would probably 

 be accompanied by the extinction of many types. That 

 changes of this character did take place during the Pleistocene 

 glacial epoch, is apparently well established. 



On the other hand, we know that luxuriant floras exist on 

 the margins and even on the surface, of living glaciers of vast 

 extent, which are not essentially different from plants of the 

 same species growing at a distance from all perennial ice. In 

 the present state of knowledge, it does not seem possible for 

 paleobotanists to designate any group or assemblage of fossil 

 plants which might not have flourished in proximity to 

 glaciers. 



While glaciers may be surrounded by a mild atmosphere, 

 congenial to plant life, the waters into which they discharge 

 either directly or after melting, are cold and could not be 

 inhabited by animals characteristic of temperate or tropical 

 climates. 



It is to be expected, therefore, that sediments laid down in 

 water into which glaciers are discharging could only contain 

 the records of faunas, exclusive of land animals, characteristic 

 of cold climates. 



Weight of the Evidence. 



Having in mind what records might reasonably be expected 

 to occur in the rocks of the Newark system, providing glaciers 

 had assisted in their deposition, let us see what the facts are : 



First. No smoothed or striated rock surfaces either in the 

 Newark system itself or on the floor on which it rests, have 

 ever been found. 



Second. No glaciated bowlders have been observed in the 

 system. 



Third. No scattered b6wlders or large rock fragments indi- 

 cating iceberg drift, have been found in the off-shore deposits. 



Fourth. No Newark fossils indicating a cold climate, even 

 in a remote way, have been discovered. 



The paucity of molluscan life has been advanced as indicat- 

 ing Arctic conditions. It is well known, however, that mol- 

 lusks and many other forms of life, inhabit the seas of northern 

 regions close to where glaciers discharge. Shells occur also in 



