The collecting data can be taken from the labels that were placed in each bag of fossils as they were collected, or from the field notebook. Actually, it is wise to check one against the other. This information should then be entered in some type of record book and also placed on a more permanent label which is put in the tray or box with the fossil. The catalog and label should contain such pertinent data as (1) the scientific name of the fossil, (2) the geologic formation from which the specimen was collected, (3) the exact geographic location of the collecting locality, (4) the name of the collector, (5) the date the fossil was collected, and (6) the catalog number of the specimen. The latter is usually placed in the upper right hand corner of the label (fig. 6) and corresponds with a like number in the record book. Specimen No. P-185 NAME Spirifer rockymontanus FORMATION Big Saline (Penn.) LOCALITY Little Brady Creek, McCulloch Co., Tex. (1000′ NE of Smith ranch House) COLLECTOR F. B. Plummer DATE July 1937 [Illustration: Fig. 6. A brachiopod showing the catalog number on it, and the accompanying label that pertains to the specimen.] The entries in the catalog should be numbered consecutively, and all specimens from the same locality should bear the same number. This number should be written on the fossil with India ink, preferably on any remaining matrix or on some inconspicuous part of the specimen (fig. 6). If the surface of the fossil is too coarse or porous for ink, the catalog number can be written on a small patch of white enamel or clear nail polish painted on the specimen. After the ink has dried it should be coated with a dab of clear shellac or clear nail polish to help preserve the number. If each specimen is numbered, it can easily be identified even if it should become separated from its label. HOW FOSSILS ARE USED Fossils are useful in a number of different ways, for each specimen provides some information about when it lived, where it lived, and how it lived. Fossils are very important, for example, in tracing the development of the plants and animals of our earth. This is possible because the fossils in the older rocks are usually primitive and relatively simple; but a study of similar specimens that lived in later geologic time shows that the fossils become progressively more complex and more advanced in the younger rocks.