1. Studies have been made of products obtained by treating several reptilian fossil bones with dilute formic acid. 2. Their amounts and compositions have been compared with those of similarly treated fresh and Pleistocene bones. 3. Fewer and small peptides are obtained from the older fossils but in only one instance was the composition significantly different from that of the total protein. 4. For the collagenous proteins aspartic acid was the most readily freed by hydrolysis; for these older proteins it is alanine. 5. Unlike the Pleistocene proteins, the chromatograms from these older proteins have always had peaks in the position of beta-alanine, and usually others of unidentified origin.