22, CHARLES R. KEVES 
If the deflative hypothesis of regional desert lowering and level- 
ing be accepted, we have in the desert ranges a stream-type hitherto 
unrecognized. The streams of this class have had no history pre- 
vious to the youthful stage of the present geographic cycle, they 
have no prospect of relations with streams of a later cycle. Their 
birth, their span of life, their extinguishment are definitely cir- 
cumscribed. They are the only existing streams we know of that 
do not have some sort of inherited relations with the waters of 
previous geographic cycles. They are the only streams the com- 
plete life histories of which may be distinctly traced. They are 
the only streams whose origin is clearly fixed in time and sharply 
limited in space. 
