[Fig. 338]
In figure 339, the only question involved is where to stop tracing. The rule is: when tracing on a ridge with an upward trend, stop at the point on the upward trend which is nearest to the right delta. X is the point in this pattern.
[Fig. 339]
In figure 340, the question involved is also one of tracing. In this pattern, the tracing is not on a ridge with an upward trend. The tracing, therefore, is continued until a point nearest to the right delta, or the right delta itself, is reached. This tracing is a meeting tracing.
[Fig. 340]
There are a few constantly recurring patterns which, though not questionable or doubtful as they appear, present a peculiarly difficult problem in classifying. The patterns referred to are usually double loops, though accidental whorls and loops sometimes present the same problems. The difficulty arises when a loop is so elongated that the recurve does not appear until near the edge of a fully rolled impression or an impression that is rolled unusually far, as in figures 341 to 344.
