CATALOGUE OF THE CRABS OF THE FAMILY PERICERID/E IN THE U. S. NATIONAL MUSEUM. Mary J. Rathbun, Department of Marine Invertebrates. (With Plates XXVIII-XL.) The classification adopted in the following catalogue is that estab-lished by Mr. E. J. Miers, in the Journal of the Linnfean Society of London V« 1. xiv, pp. 662 to 667, 1879, and modified by him in the Challenger Report, Zoology, Vol. xvn, 1886. His descriptions of Li-Mnia and PeWceranave been amended to receive new species which do not appear to be generically distinct. In the key are included all the genera supposed to belong to the family. The characters distinguishing those genera which have not been seen by the writer are inclosed in parentheses. In the key to species only those represented in the National Museum are enumer-ated. At the end of the catalogue a list is given of the species of Periceridse not in the Museum, for the benefit of future students of the group, and also to call attention to the deficiencies of the collection in the hope that it may be enriched in this direction through gifts and exchange. Of the fo: ty-eight species of Periceridte contained in the National Museum, one is European, two are East Indian, and the remainder American. Of the latter, eleven are found on the Pacific coast, from the Gulf of California to the Galapagos Islands, and thirty-four on the Atlantic coast. Of the Atlantic forms, two only range from Massa-chusetts southward. The remainder inhabit the southern Atlantic States and the West Indies, in many cases extending to Brazil. Ell-teen species are described as new, of which six are from the Gulf of California, and, with two exceptions, represented by a single specimen each. In addition to the specimens in the National Museum, the writer was enabled to examine also the Periceridie in the Museum of Union Col-lege, Schenectady, N. Y., and those contained in a collection made in the Bahama Islands by Mr. Frederick Stearns, of Detroit, Mich., in 1888, and kindly lent by him for study. The latter collection yielded an additional species, which is here described. The writer is indebted Proceedings National Museum, Vol. XV— No. 901.