304 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
meander cuts below the plain of its predecessor. The curves and cusps 
of Terrace B result from a vacillation of the meander during its 
down-valley progress; a rather sharp cusp being left between B 2 
and B 3, while the curves from B 3 to B 9 have ares so small as to 
join in a nearly straight terrace front. 
Fie. 10. 
It may be noted that the small curves 
by which a nearly straight terrace front 
is usually formed are as a rule to be ex- 
pected only towards the side of a valley, 
and less commonly on a terrace spur that 
advances into the valley. For example, 
in Figure 10 the little curves A, C, D, E, 
record so many positions of the meander 
apex, and will not now be destroyed until 
a later meander under-cuts them. Scarps 
of this kind may be called one-sweep scarps ; 
and their cusps, one-sweep cusps. Several 
similar cusps are shown in Figure 9. The 
longer curve, E E’, cut by the advancing 
front of the meandering river, may be 
abandoned if the river is diverted by a 
short-cut to a new course, and if so the 
advancing terrace spur will be smooth trimmed. 
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