1971. . Arthropoda (O, P, Q & R) Part O. Arthropoda 1: Arthropoda General Features, Protarthropoda, Euarthropoda General Features, Trilobitomorpha, xix + 560 p., 415 fig., 1959. . The original volume is out-of-print. --- Part O refers to stem-arthropods including velvet worms (Onychophora), water bears (Tardigrada), and trilobites. Part O, Revised. Arthropoda 1, Volume 1: Trilobita: Introduction, Order Agnostida & Order Redlichiida, xxiv + 530 p., 309 fig., 1997. . (Part O, Revised. Arthropoda 1: Trilobita --- additional volumes in preparation). Part P. Arthropoda 2: Chelicerata, Pycnogonida & Palaeoisopus, xvii + 181 p., 123 fig., 1955 / 1956. . --- Part P refers to extinct chelicerates including eurypterids (sea scorpions), xiphosurans (horseshoe crabs), pycnogonids (sea spiders), and arachnids. Part Q. Arthropoda 3: Crustacea & Ostracoda, xxiii + 442 p., 334 fig., 1961. . --- Parts Q and R refer to crustaceans such as crabs, lobsters, and ostracods, as well as myriapods (millipedes and centipedes), and hexapods (such as insects). (Part Q, Revised. Arthropoda 3 --- in preparation). Part R. Arthropoda 4, Volumes 1 and 2: Crustacea (exclusive of Ostracoda), Myriapoda, & Hexapoda, xxxvi + 651 p., 397 fig., 1969. . The original volume is out-of-print. Part R. Arthropoda 4, Volumes 3 and 4: Hexapoda, xxii + 655 p., 265 fig., 1992. . The original volume is out-of-print. (Part R, Revised. Arthropoda 4 --- in preparation). Echinodermata (S, T & U) Part S. Echinodermata 1, Volumes 1 and 2: Echinodermata General Features, Homalozoa, Crinozoa (exclusive of Crinoidea), xxx + 650 p., 400 fig., 1967 / 1968. . The original volume is out-of-print. ---- Part S refers to primitive sessile echinoderms. Part T. Echinodermata 2, Volumes 1-3: Crinoidea, xxxviii + 1,027 p., 619 fig., 1978. . The original volume is out-of-print. ---- Part T refers to crinoids, a group of echinoderms including living sea lilies. Part T, Revised. Echinodermata 2, Volume 3: Crinoidea, xxix + 261 p., 112 fig., 2011. . Part U. Echinodermata 3, Volumes 1 and 2: Asterozoans & Echinozoans, xxx + 695 p., 534 fig., 1966. . ---- Part U refers to asterozoans (including sea stars and brittle stars) and echinozoans (including sea urchins and sea cucumbers). Graptolithina (V) Part V. Graptolithina, with sections on Enteropneusta & Pterobranchia, xvii + 101 p., 72 fig., 1955. . The original volume is out-of-print. --- Part V refers to the extinct graptolites, as well as to other hemichordates. Part V, Revised. Graptolithina,