species, in a peculiar and rather saline 

 habitat. 3 



In the summer of 1920 the writers visited 

 the Ice Spring Craters lava field of the Sevier 

 Desert in the ancient Lake Bonneville basin 

 described in detail by Gilbert. 4 On climbing 

 down into the old lava vent 5 of the Terrace 

 crater we were surprised to find a small 

 crustacean abundant in the small pool of 

 clear water at the bottom. It was noted that 

 a number of the animals were very slightly 

 pigmented, apparently indicating that in the 

 semi-darkness of the pool they were approach 

 ing cave conditions. In all instances, how 

 ever, the eyes were fully pigmented. The 

 presence of the Gammerus led to the assump 

 tion that the water was non-saline and we 

 were preparing to replenish our water bag 

 when taste showed it to be distinctly brackish. 



A sample of the water was therefore taken 

 in a clean Mason fruit jar from which it was 

 afterwards transferred to citrate bottles for 

 shipment to the laboratory. The water had 

 a freezing point lowering of 0.410 C., indi 

 cating an osmotic concentration of 4.94 

 atmospheres and an electrical conductivity of 

 .0138 reciprocal ohm. The hydrogen ion con 

 centration of the water (determined electro- 

 metrically) was CH = 0.409 X 10 7 = P H 7 -388. 

 Analysis showed the following composition. 



s The genus Gammerus has species which occur 

 in more or less saline coastal habitats and in non- 

 saline inland waters. 



* Gilbert, G. K., &quot;Survey West of the 100th 

 Meridian,&quot; Vol. 3, pp. 136-144; also &quot;Lake 

 Bonneville,&quot; Monographs U. S. GeoL Survey, I., 

 pp. 320-325, 1890. 



6 The lava vent is a circular tube, at one side of 

 the wide crater, about 12 feet in diameter inclined 

 10 or 15 from the vertical. It can be explored 

 /or about 25 feet when progress is stopped by 

 water. 



