The Terrace crater, and indeed all of the 

 craters of the Ice Spring Craters group, is un 

 questionably post-Bonneville in origin. There 

 is no trace of wave work on the outer slopes 

 of the craters such as are so conspicuous on 

 Pavant Butte to the north, and neither lacus 

 trine sediments nor evidences of subaqueous 

 erosion appear on the surface of the evidently 

 recent lava fields as they do on the Fumarole 

 Butte lava field to the northwest. 



The depth of the vent of the Terrace crater 

 is 260 feet below its general rim and 220 feet 

 below the sill of the last outflow. The prob 

 lem of the original introduction of Gammerus 

 into the small pool of water occupying the 

 bottom of this crater is that of the transpor 

 tation of small crustacean species or their 

 eggs in general. The point of physiological 

 interest is the occurrence of this species, 

 hitherto reported from non-saline waters, in 

 water of this concentration. 



ROSS AlKEN GORTNER, 



Division of Agricultural Biochemistry, Uni 

 versity of Minnesota, 



J. ARTHUR HARRIS, 



Station for Experimental Evolution, Car 

 negie Institution of Washington 



purely empirical and also when one considers that 

 in some instances the actual analytical values, and 

 consequently accompanying experimental errors, 

 were multiplied by 50 to bring the calculation to a 



liter basis. 



