They are described as the whorl, the loop, and the arch. Arches are described as either simple or tented. Simple arches sweep across the fingertip without a triradius or change in direction. Loops have at least one recurring ridge, a triradius, and a ridge cound of at least one across a recurving ridge. Ulnar loops are those that have their ridges entering or leaving on the ulnar side of the hand.
Radial loops have their ridges entering or leaving on the radial side of the hand.
In any case, the loops will vary according to size, and shape, but all will have only on triradius. Referring to figure 1c on the following page,look at diagram c, the loop. This diagram has a triradius drawn which has fifteen as its ridge count. Count the number of ridges that cross that triradius. When referring to diagrams d,e, and f on the same figure, note that there are two triradii drawn.