erential choice between the two looping ridges. It is arbitrarily
given the classification of a tented arch.

In figure 307, the difficulty lies in locating the delta. The only
ridges answering the definition of type lines (ridges running parallel
and then diverging to enclose the pattern area) have three ending
ridges between them. The type lines, the delta, and the core are
located as indicated. The pattern is classified as a six-count loop.

Figure 308 is classified as a tented arch, although it appears at
first glance to be a loop. Closer inspection shows that the looping
ridge does not tend to go out the side from which it entered but
rather seems to proceed downward ending in an abutment forming a
definite angle of 90 deg..

[Illustration: 307]

[Illustration: 308]

[Illustration: 309]

[Illustration: 310]

[Illustration: 311]

In figure 309, an impression is shown which at first appears to be a
loop. Closer inspection will show that one of the elements of the loop
type is missing, namely, a ridge count across a looping ridge; for it
is to be borne in mind that the recurve of the innermost loop should
be free of appendages abutting between the shoulders at right angles.
The core, in this illustration, therefore, is placed where the
appendage of the innermost loop touches the next ridge which is a good
recurve. If an imaginary line is placed between delta and core, it
will be seen that there are no intervening ridges; hence, there is no
ridge count.

Figure 310 is a pattern which contains two elements of a loop but
lacks the third. It is classified as a tented arch. Thus an impression
having a delta and a recurve, but not having a ridge count across a
looping ridge, falls into this classification.

It will be noticed that although this pattern has the resemblance of a
plain arch, the center of the impression actually contains a partially
formed loop. A recurving ridge enters from the right side and exits in
the same direction. A delta also appears just below the recurve. In
attempting to obtain a ridge count, it is seen that the imaginary
line drawn between the delta and the core runs directly along the
ridge emanating from the former and which is joined onto the side of
the recurving ridge. For this reason, no ridge count is possible.

[Illustration: 312]

Figure 311 is a tented arch. There are three loop formations, each one
of which is spoiled by an appendage abutting upon its recurve between
th