o be classified with the
tented arches. In figure 189, the only possible delta must be placed
upon the looping ridge, thus preventing a ridge count although delta
and recurve are present. Figure 190 is assigned the classification of
a tented arch. One of the requirements of a loop type is that the
ridge enters on one side, recurves, and makes its exit on the side
from which it entered. This, of course, makes it necessary that the
ridge pass between the delta and the core. It will be noted from this
figure that although this ridge passes between the delta and the core,
it does not show any tendency to make its exit on the side from which
it entered, and therefore the loop classification is precluded, and it
is a tented arch.

_The whorl_

The patterns to which numerical values are assigned in deriving the
"primary" in the extension of the Henry System of fingerprint
classification used by the Federal Bureau of Investigation are the
whorl-type patterns, which occur in about 30 percent of all
fingerprints.

_The whorl is that type of pattern in which at least two deltas are
present with a recurve in front in each._ Figures 191 to 193 reflect
the minimum requirements for the whorl.

[Illustration: 191]

[Illustration: 192]

[Illustration: 193]

It is important to note that the above definition is very general;
however, this pattern may be subdivided for extension purposes in
large groups where whorls are predominant. Even though this extension
may be used, all types of whorls are grouped together under the
general classification of "Whorl" and are designated by the letter
"W".

The aforementioned subdivisions are as follows: The Plain Whorl, The
Central Pocket Loop, The Double Loop, and The Accidental.

_The plain whorl_

The "plain whorl" consists of the simplest form of whorl construction
and is the most common of the whorl subdivisions. It is designated by
the symbol "W" for both general classification and extension purposes.

_The plain whorl has two deltas and at least one ridge making a
complete circuit, which may be spiral, oval, circular, or any variant
of a circle. An imaginary line drawn between the two deltas must touch
or cross at least one of the recurving ridges within the inner pattern
area. A recurving ridge, however, which has an appendage connected
with it in the line of flow cannot be construed as a circuit. An
appendage connected at that point is considered to spoil the recurve
on th