THE CANCROID CRABS OF AMERICA 



By Mary J. Rathbun 

 Associate in Zoology, United States National Museum 



INTRODUCTION 



This volume is the third of the series of handbooks on American 

 crabs. The first volume ''The Grapsoid Crabs of America" foi-ms 

 Bulletin 97, and the second volume "The Spider Crabs of America" 

 forms Bulletin 129, of the U. S. National Museum. The introduc- 

 tory remarks in Bulletin 97, relating to sources of material, special 

 researches, acknowledgments, and glossary of terms apply to the 

 present work also. 



In recent years the Museum has been enriched by vast collections 

 of crabs from South America obtained by Dr. Waldo L. Schmitt in 

 the course of two extended series of explorations in South American 

 waters under the auspices of the Walter Rathbone Bacon scholar- 

 ship. Besides the material collected, Doctor Schmitt was able to 

 arrange advantageous exchanges with various South American 

 museums and when that was not feasible, to borrow for study. In 

 this way many gaps in this Museum were filled, both as to species 

 and numbers, and our knowledge of the fauna greatly increased. 

 Among the valuable discoveries was an example of the insignificant 

 little crab, Metopocarcinus truncatus Stimpson, of which the type is 

 not extant and no other specimen is known to exist in any collection. 

 More striking is the discovery of a giant Cancer on the Atlantic 

 coast of South America, the property of the Museu Paulista. Through 

 the courtesy of the assistente. Dr. H. Luederwaldt, the author is 

 permitted to describe this species from a series of excellent photo- 

 graphs. The carapace has a width of 25 cm. (9.5 inches) and is the 

 largest American species known. 



Next in importance are the investigations made through several 

 seasons for the Carnegie Institution by Doctor Schmitt and Mr. 

 Clarence R. Shoemaker at the Tortugas and vicinity, in cooperation 

 with Dr. Wilham H. Longley in charge of the laboratory. These 

 have provided long series of various forms and have extended the 

 range of many, aside from the primary object of the inquiry, to 

 ascertain the food habits of fishes. The Universit}'' of Southern 

 California and the California Academy of Sciences have submitted 

 special collections from the Pacific coast, the result of which, so far 

 as the Cancroidea are concerned, are recorded here. 



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