It can be ascertained that the pattern in figure 376 is a loop, but an accurate ridge count cannot be obtained because the left delta does not appear. The approximate ridge count of this loop is 14 to 16. This approximation is sufficient for a fingerprint expert to place this loop in the "O" group of any finger of the subsecondary. The correct ridge count of this loop is 19, and it appears in illustration 377. The approximate ridge count is not sufficient to place this print properly in the large files of the FBI because in certain general complete classification formulas the accurate ridge count is needed to obtain an extension. These extensions use a smaller grouping of ridge counts to form a valuation table, and in this way, differ from the larger grouping of ridge counts which form the basis of the subsecondary classification. These extensions are called the second subsecondary and the special loop extension and are outlined in chapter VI. [Illustration: 374. Improper.] [Illustration: 375. Proper.] [Illustration: 376. Improper.] [Illustration: 377. Proper.] There are two additional points which illustrate the FBI's need for the delta, ridges, and core to show clearly in loops. The first point is set forth: the ridge count of the loop may be needed to obtain the key classification. The key classification is an actual ridge count, and no valuation table is used to obtain a subdivision. The key classification is used as an integral part of the fingerprint filing system. The second point is as follows: the ridge count may be needed to obtain the final classification. The final classification is an actual ridge count, and no valuation table is used to obtain a subdivision. The final classification is used as an integral part of the fingerprint filing system. The following are just a few examples to illustrate the completeness of the classification formula used in the FBI fingerprint file: 12 M 9 R OIO 11 S 1 R IOI Key Major Primary Secondary Subsecondary Final 6 17 aW IIO 9 1 U OII Key Primary Small letter Subsecondary Final Secondary 8 S 1 Ua II 6 S 1 U III Key Major Primary Small letter (Subsecondary Final Secondary Extension) SML (Second SML Subsecondary) 5 0 5 U IOO 14 I 17 U IOO Key Major Primary Secondary Subsecondary Final