THE GRAPSOID CRABS OF AMERICA. 



By MART J. RATHBUN, 

 Associate in Zoology, United States National Museum. 



INTRODUCTION. 



This volume is part of a work projected many years ago as a hand- 

 book for the study of American crabs, the main purpose being to 

 give a brief description with figures of each species. In the mean- 

 time the character of the work has been somewhat changed so as to 

 include a detailed catalogue of the specimens 'in the United States 

 National Museum. Unavoidable delay in preparation has led to an 

 accumulation of material which has greatly augmented the number 

 of known species. As a result the work has been expanded into four 

 volumes, of which the present one, dealing with the Grapsoids or 

 Catometopes, is the first. 



SOURCES OF MATERIAL. 



The collections in the United States National Museum form the 

 basis of this bulletin. They consist chiefly of material obtained by 

 United States Government bureaus, such as the Bureau of Fisheries 

 (known previous to July 1, 1903, as the United States Fish Commis- 

 sion). Through the activities of its various vessels and laboratories 

 the Bureau of Fisheries has been able to transfer to the National 

 Museum vast accumulations from nearly all the coasts of America. 

 The amount of work accomplished by the steamers Albatross and 

 Fish Hawk and the schooner Grampus, as well as by other vessels 

 of the commission in earlier years, is indicated in the detailed lists of 

 specimens. 



Other Government explorations that have yielded considerable 

 results are those constantly carried on by the Bureau of Biological 

 Survey of the Department of Agriculture and those occasional ex- 

 peditions under the auspices of the National Museum itself and the 

 Smithsonian Institution. Of the Crustacea obtained by the United 

 States exploring expedition in 1838-1842 and by the North Pacific 

 exploring expedition in 1853-1856 very little remains, owing to the 

 inadequate housing of the former collection before the existence of 

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