In 1897 C. E. Beecher published his “Outline of a Natural Classification of the Trilobites”, which has since “proved superior to any previously proposed”. If early a score of years have passed since that time and many new Trilobites have been discovered, the majority of which fit into this system without difficulty and prove that to a large extent it is conceived on a sound basis. A few, however, do not fit in and have therefore revealed in it weaknesses, the existence of which tend to hinder the systematic study of Trilobites. In the following pages it is proposed to point out these weaknesses and to make suggestions for modifying and extending Beecher's system upon what it is hoped will prove to be natural lines.