4 BULLETIN 166, UNITED STATES NATIONAL MUSEUM 



ADDITIONAL ABBREVIATIONS AND NOTES 



In the lists under "Material examined" and elsewhere, a number in 

 parentheses following an indication of a specimen or specimens de- 

 notes a catalog number of the United States National Museum unless 

 otherwise indicated. M. C. Z.= Museum of Comparative Zoology; 

 P. M. Y. U. = Peabody Museum of Yale University ; S. U. I. = Museum 

 of the State University of Iowa; Mus. Paulista is at Sao Paulo, 

 Brazil; the words "U. S. Fisheries Steamer" should be understood 

 before Albatross, Fish Hawk, Grampus, and Speedwell; and "U. S. 

 Coast Survey Steamer" before Bache, Blake, and Hassler; Zaca= 

 Croker Expedition, California Academy of Sciences; Anton Dohrn 

 in the Atlantic = Carnegie Institution; Anton Dohrn in the Pacific = 

 Venice Marine Biological Station, University of California; y=young. 



In the color notes made by Dr. Schmitt, the 1886 edition of Ridg- 

 way's "Nomenclature of Colors" is used. 



THE OXYSTOMATOUS AND ALLIED CRABS OF AMERICA 



Of the crabs treated in this volume, the Gymnopleura are the most 

 unique and the most primitive, being derived from the Macrura.^ 

 The anterior thoracic sterna are broad, the posterior narrow and 

 keel-Uke, carapace elongate in the shape of an urn, the last pair of 

 legs reduced and dorsal in position. Represented in America by 

 only four genera. 



The Dromiacea include the "hairy crabs", wliich are typically 

 subglobose, and others that are subquadrate, but all with a narrow 

 front. The outer maxiUipeds have the merus and iscliium sub- 

 quadrangular. The last one or two pairs of feet are small and 

 subdorsal and hold jn place a sponge, ascidian, or shell, which is 

 used for concealment. The subtribe contains two superfamilies, in 

 one of which the eyes are 2-3ointed. 



The Oxyptomata are by far the largest group represented. They 

 include the circular or ball-shaped crabs, the box or shame-faced 

 crabs, and the smaller, usually flat and shield-shaped dorippids, or 

 mask crabs, in which the legs of the last two pairs are short, slender, 

 and elevated. In the oxystomes the mouth parts taper narrowly 

 toward the front. The Calappidae, or shame-faced crabs, are 

 distinguished by their large chelae, which when closed spread over 

 the anterior part of the ventral surface. 



The subtribe Hapalocarcinidea is represented on this continent by 

 two genera and species, both of which live in coral galls. Its position 

 in the Brachyura has not been definitely determined. 



The single example of the subtribe Brachygnatha is inserted here 

 because it was accidentally omitted from Bulletin 97, "The Grapsoid 

 Crabs of America", Geryon guinquedens, p. 266. 



' See Bourne, The Raninidae, Journ. Linn. Soc. London, Zool., vol. 35, p. 25, 1922. 



