The purpose of this paper is to evaluate relationships in the light of morphological and paleontological evidence, and to propose an evolutionary scheme which accounts for the present distribution of extant palinurid species. The spiny lobsters, because of their large size, commercial importance, benthic habits as adults and pelagic habit as larvae, and their wide geographic and vertical distribution, are well suited for a study of evolution in the marine environment. In 1946 Holthuis provided an excellent basic taxonomic revision of the Palinuridae and, sometimes with colleagues, he followed this up with more detailed studies of smaller groups within the family, particularly in the genus Panulirus. But some of the less well known genera inhabiting deeper waters still require revision and for this reason it has been necessary to include some taxonomic discussion in the paper; this has been kept to a minimum and will be reported on more fully in an appropriate publication at a later date. The deficiencies in our knowledge of palinurid systematics and evolution have been realized by Glaessner (1960) who stated (p. 42), "There is still some doubt about homologies and evolution in the Scyllaridea [Palinuridae and Scyllaridae] . . . for which groups more morphological information on recent and fossil forms is required." We have attempted to overcome these deficiencies and to present speciation mechanisms applicable to the marine environment.