The classification of trilobites is discussed. No orders (or suborders), but a number of superfamilies are recognized and discussed. The Zacanthoidacea, Olenellacea, Redlichiacea, and Conocoryphaoea may have developed from a common trilobite stock with dorsial shield. The Agnostacea ( comprising Agnostidae and Eodiscidae) may be close to an early Redlichiacean-Conocoryphacean stock. The Asaphacea, Dikeiocephalacea, Odontopleuracea, Phacopacea, and Cheiruracea are claimed to be most probably descendents of the Conocoryphacea, and the same is likely true of the Raphiophoracea. The Lichidae and Telephidae are suspected of being related to the Odontopleuracea, and so is Pharostoma, which may belong to a lineage between this superfamilly and Calymenaoea. Attention is drawn to the pattern of the glabellar furrows and the anterior sutures as features of classiticatory importance, while other features, such as size of pygidium and length of eyes are not considered of as great a taxonomic value as hitherto. A list (p. 205) shows the trilobite families arranged in superfamilies. A table (F1ig. 2, p. 207) sugests the possible relationships of the major groups of trilobites.