Terrestrial and Littoral Amphipods of the Genus Orchestia, Family Talitridae.* This is No. 16 of the series “Studies on the New Zealand Amphipodan Fauna”, and is part of an investigation carried out at the Zoology Department, Victoria University College, Wellington, during the tenure of a New Zealand University Research Fund Fellowship. By D. E. Hurley [Received by the Editor, December 17, 1956.] Abstract The generic status of Orchestia and Parorchestia is discussed and Parorchestia is considered a synonym of Orchestia. Keys are given to the 14 species of New Zealand Orchestia here described, four of which are new to science. Introduction and Acknowledgments The genus Orchestia includes both littoral and terrestrial species of amphipods. The terrestrial species are especially interesting because of their importance in the leafmould fauna of the forests of New Zealand and other Pacific countries. One species of terrestrial amphipod belonging to another genus has already been recorded from New Zealand (Hurley, 1955), and it is my intention to treat the terrestrial species from a more general point of view in a subsequent paper. I wish to thank Professor Percival and the Canterbury University College Council and library for access to the late Professor Chilton's specimens and literature. Other specimens and collections have been made available by the Dominion Museum and Canterbury Museum, and I am grateful also to those individual collectors who have donated material. As in all of these studies, I am indebted to the library staff at Victoria University College, and especially to Miss M. Wood, of the Royal Society Library. I wish to thank Professor L. R. Richardson, of Victoria University College, under whose guidance and supervision this work was originally carried out. Its speedier completion has been made possible through the kind permission of Mr. J. Brodie, of the New Zealand Oceanographic Institute. Genus Orchestia Leach. Orchestia Leach, 1813–14: 402; Stebbing, 1906: 530. Parorchestia Stebbing. 1899: 402; Stebbing, 1906: 557; Shoemaker, 1942: 17. “Like Talitrus except that gnathopod 1 in male and female is less strongly developed and subchelate instead of simple; gnathopod 2, male, powerfully subchelate instead of feebly chelate. Maxillipeds with 4th segment of palp absent, rudimentary or small; front lobe of sideplate 5 may be as deep as sideplate 4. Notching of dactylos in peraeopod 2 seldom as sharp and decided as in Talorchestia.” —Adapted from Stebbing, 1906. Stebbing (1906) defined Parorchestia as “Like Orchestia but maxillipeds with 4th joint of palp distinct, though very small, conical and having a spine on the truncate apex.” This definition was not satisfactory for long. Chilton (1909) commented: “In Orchestia, however, the maxillipeds may, as Stebbing himself states, have an obscure rudiment of the fourth joint of the palp, and the presence or absence of