When interpreting a pattern consisting of two ending ridges and a delta but lacking a recurve, do not confuse the ridge count of the tented arch with that of the ridge count for the loop. The ridge count of the tented arch is merely a convention of fingerprinting, a fiction designed to facilitate a scientific classification of tented arches, and has no connection with a loop. To obtain a true ridge count there must be a looping ridge which is crossed freely by an imaginary line drawn between the delta and the core. The ridge count referred to as such in connection with the tented arches possessing ending ridges and no recurve is obtained by imagining that the ending ridges are joined by a recurve only for the purpose of locating the core and obtaining a ridge count. If this point is secure in the mind of the classifier, little difficulty will be encountered. Figures 140 and 141, then, are tented arches because they have two of the characteristics of a loop, delta and ridge count, but lack the third, the recurve. [Illustration: 142] [Illustration: 143] Figure 142 is a loop formation connected with the delta but having no ridge count across a looping ridge. By drawing an imaginary line from the core, which is at the top of the rod in the center of the pattern, to the delta, it will be noted that there is no recurving ridge passing between this rod and the delta; and, therefore, no ridge count can result. This pattern is classified as a tented arch. There must be a white space between the delta and the first ridge counted, or it may not be counted. Figure 143 is also a tented arch because no ridge count across a looping ridge can be obtained, the bifurcations being connected to each other and to the loop in a straight line between delta and core. The looping ridge is not crossed freely. No white space intervenes between the delta and the loop. These patterns are tented arches because they possess two of the characteristics of a loop, a delta and a recurve, but lack the third, a ridge count across a looping ridge. Figure 144 is a tented arch combining two of the types. There is an angle formed by ridge _a_ abutting upon ridge _b_. There are also the elements of the type approaching a loop, as it has a delta and ridge count but lacks a recurve. [Illustration: 144] [Illustration: 145] [Illustration: 146] Figures 145 to 148 are tented arches because of the angles formed by the abutting ridges at the center of the patterns. Figure 149 is a tented arch because of the upthrust present at the center of the pattern. The presence of the slightest upthrust at the center of the impression is enough to make a pattern a tented arch. [Illustration: 147] [Illustration: 148] [Illustration: 149] [Illustration: 150] An upthrust must be an ending ridge. If continuous as in figure 150, no angle being present, the pattern is classified as a plain arch. Figures 151 to 153 are plain arches. Figure 154 is a tented arch.