The discoveries and investigations of palæontologists touching the question of ambulatory and branchigerous appendages of the Trilobites have been entirely ignored by many of the ablest workers in the science. The important evidence which Mr. Billings produced was unsatisfactory to both Dana and Verrill. In 1881, after many years of untiring labour, Mr. C. D. Walcott (in the “Bulletin of the Museum of Comparative Zoology at Cambridge College”) furnished most conclusive proof of the existence of appendages to the cephalic, thoracic, and abdominal divisions of Calymene, Ceraurus, and Acidaspis. He says: “the discoveries have been received in about the same manner” as those of Billings and others—with incredulity, and as “having little value.”