D. Guinot (Muséum national d’Histoire naturelle, Paris); R.B. Manning (late of Smithsonian Institution, U.S. National Museum of Natural History, Washington, D.C.); J. Martin (Los Angeles County Museum, California); and P.K.L. Ng (National University of Singapore) each have provided helpful comments about the groups under discussion here; our thanks to them. We thank C. Beschin and A. De Angeli (Museo Civico 'G. Zannato', Italy); S. Calzada and P. Artal (Museo Geológico del Seminario de Barcelona, Spain); A. Kollar (Carnegie Museum of Natural History, Pittsburgh, Pennsylvania); T. Komai and H. Kato (Natural History Museum and Institute, Chiba, Japan); R. Lemaitre and W.C. Blow (Smithsonian Institution, U.S. National Museum of Natural History, Washington, D.C.); P. Müller (Hungarian Geological Survey, Hungary); T. Naruse (University of Ryukyus, Japan); A. Rage (Muséum national d’Histoire naturelle, Paris); and T. Sato (Kanagawa Prefectural Museum of Natural History, Japan) for loans from or access to collections in their institutions. J. Jagt, Natuurhistorisch Museum Maastricht, the Netherlands, provided important information about Titanocarcinus ; our thanks to him.Sasagawa Scientific Research Grant from the Japan Science Society (no. 10-396M and 11-397M) and a Grant-in-Aid for Scientific Research from the Ministry of Education, Science, Sports and Culture (no. 10916027) supported fieldwork in the Ryukyus Islands to Karasawa. Travel for examination of Hungarian fossils was provided by a special fund from the Mizunami Municipal Government to Karasawa. Travel for collection of fossils in Croatia and Austria and to examine material deposited in museums in Budapest and Spain was provided by the Department of Research and Graduate Studies, Kent State University, to Schweitzer. Travel for examination of material in museums in Japan and in the United Kingdom was funded by National Geographic Society Grant 6265-98 to Schweitzer and Feldmann. NSF Grant INT 0003058 to Feldmann and Schweit-zer funded collection of relevant material in Baja California Sur, México. Feldmann read an earlier draft of the manuscript; his suggestions are much appreciated. Very constructive reviews were provided by F.R. Schram, Langley, Washington, USA, and an anonymous reviewer; our thanks to them. M. Keatts, LAN Technician, Department of Geology, Kent State University, assisted with computer-related issues. The Inter-Library Loan service at Kent State University provided invaluable assistance in helping to locate old and obscure literature relevant to this study.