Acknowledgments

We would like to thank the following persons for allowing us to use specimens and facilities under their care: Dr Donn E. Rosen, American Museum of Natural History; Dr Bruce Welton, Chevron Oil Field Research Co., La Habra, California; Dr Loren P. Woods, Field Museum of Natural History; Drs Camm Swift and Robert Lavenberg, Los Angeles County Museum of Natural History; Dr Richard H. Rosenblatt, Scripps Institution of Oceanography; Prof. George S. Myers and Dr Warren C. Freihofer, Division of Systematic Biology, Stanford University; Dr Boyd Walker, University of California at Los Angeles; Dr Shelton P. Applegate, Department of Paleontology, Instituto de Geologia, Universidad Nacional Autonomica de Mexico and Dr Leonard P. Schultz, Division of Fishes, U.S. National Museum.

In addition, Mr Stewart Springer (then of the National Marine Fisheries Service Systematics Laboratory, U.S. National Museum) gave Compagno a specimen of Nasolamia velox (LJVC-0268) that was used in anatomical investigations. Peter A. McCrery did the dentition illustrations of N. velox, and Dr Victor G. Springer of the Division of Fishes, U.S. National Museum allowed us to use these illustrations for this paper. Mrs Martha J. Mitchell of Kent Cambridge Scientific Instrument Co. and Stanford University permitted Compagno to use a Cambridge Stereoscan scanning electron microscope under her care.

Compagno's contribution to this paper was part of a Ph.D. thesis project on systematics of carcharhinoid sharks researched at the Division of Systematic Biology, Stanford University, under supervision of Professor George S. Myers. This work was funded by a National Defence Education Act Predoctoral Fellowship, National Science Foundation Predoctoral Fellowship, and Stanford Department of Biological Sciences Fellowship; all administered through the Department of Biological Sciences, Stanford University. Garrick's contribution was made possible through funds and facilities organised and administered by Dr Leonard P. Schultz of the U.S. National Museum. His work was supported by Atomic Energy Commission Contract AT(30-1) 2409 and by National Science Foundation Grant GB-245.