PROCEEDINGS OF THE UNITED STATES NATIONAL MUSEUM 



SMITHSONIAN INSTITUTION 



U. S. NATIONAL MUSEUM 



Vol. 108 Wa.hmgton : 1958 No. 3399 



REVISION OF THE MILLIPED GENUS PACHYDESMUS 

 (POLYDESMIDA: XYSTODESMIDAE) 



By Richard L. Hoffman 



Southeastern United States, from South Carolina and Tennessee to 

 Louisiana, is the home of Pachydesmus, a xystodesmid genus whose 

 species include the largest known polydesmoids of North America. 

 Despite their great size and the relatively wide range of the group, 

 however, individuals of Pachydesmus appear to be scarce or secretive. 

 Since the first species was appropriately named Polydesmus crassicutis 

 by H. C. Wood in 1864, only nine names have subsequently been 

 founded upon members of the genus, and less than a hundred speci- 

 mens are at present contained in the major collections. 



It is, in a way, fortunate that no more extensive work has been done 

 on the genus — at least work of the careless descriptive kind which has 

 been characteristic of American diplopodology and which is still being 

 published by a few investigators. Although no attempt has ever been 

 made to assemble what is known about Pachydesmus, and the pub- 

 lished descriptions and drawings are nearly useless for comparative 

 purposes, the scarcity of specimens has at least limited the confusion 

 to a fraction of that which prevails in certain other genera. 



The general plan of the present study is not pretentious. The two 

 primary considerations affecting its course have been the evaluation 

 of all specific names based upon pachydesmids and the provision of 

 accurate illustrations of those forms which appear to be valid — these 

 being the aspects of diplopod taxonomy most in need of immediate 



" Department of Biology, Virginia Polytechnic Institute, Blacksburg, Va. 



455980—58 1 181 



