Transcriber's Notes Text emphasis is denoted as _Text_ for italic and =Text= for bold. Whole and fractional parts are shown as 4-2/3. OE and oe ligature converted to Oe and oe respectively. * * * * * MEMOIRS OF THE CONNECTICUT ACADEMY OF ARTS AND SCIENCES VOLUME VII DECEMBER, 1920 The Appendages, Anatomy, and Relationships of Trilobites BY PERCY E. RAYMOND, Ph.D. ASSOCIATE PROFESSOR OF PALAEONTOLOGY, AND CURATOR OF INVERTEBRATE PALAEONTOLOGY IN THE MUSEUM OF COMPARATIVE ZOOLOGY, HARVARD UNIVERSITY [Illustration: (logo)] NEW HAVEN, CONNECTICUT PUBLISHED BY THE CONNECTICUT ACADEMY OF ARTS AND SCIENCES AND TO BE OBTAINED ALSO FROM THE YALE UNIVERSITY PRESS [Illustration (photo)] [Illustration (signature)] MEMOIRS OF THE CONNECTICUT ACADEMY OF ARTS AND SCIENCES VOLUME VII DECEMBER, 1920 The Appendages, Anatomy, and Relationships of Trilobites BY PERCY E. RAYMOND, Ph.D. ASSOCIATE PROFESSOR OF PALAEONTOLOGY, AND CURATOR OF INVERTEBRATE PALAEONTOLOGY IN THE MUSEUM OF COMPARATIVE ZOOLOGY, HARVARD UNIVERSITY [Illustration: (logo)] NEW HAVEN, CONNECTICUT PUBLISHED BY THE CONNECTICUT ACADEMY OF ARTS AND SCIENCES AND TO BE OBTAINED ALSO FROM THE YALE UNIVERSITY PRESS THE TUTTLE, MOREHOUSE & TAYLOR COMPANY TO THE MEMORY OF CHARLES EMERSON BEECHER SKILLFUL WITH HAND, BRAIN, AND PEN; REVEALER OF THE MYSTERIES OF TRILOBITES; THIS MEMOIR IS DEDICATED FOREWORD. By CHARLES SCHUCHERT. Trilobites are among the most interesting of invertebrate fossils and have long attracted the attention of amateur collectors and men of science. These "three-lobed minerals" have been mentioned or described in books at least since 1698 and now several thousand species are known to palæontologists. To this group of students they are the most characteristic animals of the seas of Palæozoic time, and even though they are usually preserved as dismembered parts, thousands upon thousands of "whole ones" are stored in the museums of the world. By "whole ones" perfect individuals are not meant, for before they became fossils the wear and tear of their time and the process of decomposition had taken away all the softer parts and even most of the harder exterior covering. What is usually preserved and revealed to us when the trilobites weather out of the embrace of their entombing rocks is the test, the hard shell of the upper or dorsal side. From time to time fragments of the under or limb-bearing side had been discovered, first by Elkanah Billings, but before 1876 there was no known place to which one could go to dig out of the ground trilobites retaining the parts of the ventral side.