tions and that wherever one of the formations mentioned
in the definition of a delta may be, it must be located midway between
two diverging type lines at or just in front of where they diverge in
order to satisfy the definition and qualify as a delta.

When there is a choice between two or more possible deltas, the
following rules govern:

- _The delta may not be located at a bifurcation which does
not open toward the core._

In figure 26, the bifurcation at E is closer to the core than the
bifurcation at D. However, E is not immediately in front of the
divergence of the type lines and it _does not_ open toward the core.
A--A and B--B are the only possible type lines in this sketch and it
follows, therefore, that the bifurcation at D must be called the
delta. The first ridge count would be ridge C.

- _When there is a choice between a bifurcation and another
type of delta, the bifurcation is selected._

A problem of this type is shown in figure 27. The dot, A, and the
bifurcation are equally close to the divergence of the type lines, but
the bifurcation is selected as the delta. The ridges marked "T" are
the type lines.

[Illustration: 27]

[Illustration: 28]

- _When there are two or more possible deltas which conform
to the definition, the one nearest the core is chosen._

Prints are sometimes found wherein a single ridge enters the pattern
area with two or more bifurcations opening toward the core. Figure 28
is an example of this. Ridge A enters the pattern area and bifurcates
at points X and D. The bifurcation at D, which is the closer to the
core, is the delta and conforms to the rule for deltas. A--A and B--B
are the type lines. A bifurcation which does not conform to the
definition should not be considered as a delta irrespective of its
distance from the core.

- _The delta may not be located in the middle of a ridge
running between the type lines toward the core, but at the
nearer end only._

The location of the delta in this case depends entirely upon the point
of origin of the ridge running between the type lines toward the core.
If the ridge is entirely within the pattern area, the delta is located
at the end nearer the point of divergence of the type lines. Figure 29
is an example of this kind.

[Illustration: 29]

[Illustration: 30]

If the ridge enters the pattern area from a point below the divergence
of the type lines, however, the delta m