2 PROCEEDINGS OF THE NATIONAL MUSEUM vol, 108 



iD individuals; because of the localization of most species which en- 

 hances their value in evolutionary studies; and because of the rela- 

 tive case of obtaining specimens for study. This last factor is par- 

 ticularly true in the case of those genera confined to the Southern 

 Appalachians. 



The present study is devoted to Dixioria, a small genus of attrac- 

 tively colored diplopods which is restricted to the Southern Appa- 

 lachians in western North Carolina, eastern Tennessee, and south- 

 western Virginia. Occurring in a very deeply dissected mountain 

 region, the forms of Dixioria are quite localized and afford interesting 

 material for the study of distribution and phjdogeny. 



My original plan to revise all of the xystodesmid genera in a single 

 publication has been abandoned, as it became obvious that such an 

 endeavor would necessarily be postponed for many years. It seemed 

 best to reserve a general treatment of generic relationships and evolu- 

 tion to serve as a culmination, rather than initiation, of the series. 



Materials and Methods 



For this study I have examined approximately 100 specimens, 

 representing all of the seven recognized forms of Dixioria and includ- 

 ing the type specimens of the two previously named species. Five 

 additional names are proposed herein. I have personally collected 

 material of all of the forms except Dixioria pela brooksi and D. dac- 

 tylijera, and this field experience has been particularly useful in pro- 

 viding fu'st-hand knowledge of the physiographic factors influencing 

 distribution. 



Most of the specimens have been collected by me or by friends, 

 but additional material has been examined from the collections of 

 several museums. Abbreviations used in the text to designate the 

 sources of preserved study specimens are as follows: 



AMNH, American Museum of Natural History, New York, N. Y. 

 CM, Carnegie Museum, Pittsburgh, Pa. 

 MCZ, Museum of Comparative Zoology, Cambridge, Mass. 

 RLH, Private collection of R. L. Hoffman, Blacksburg, Va. 

 USNM, United States National Museum, Washington, D. C. 



The drawings were made from gonopods immersed in alcohol, using 

 a binocular microscope equipped with an ocular grid. This attach- 

 ment facilitated very accurate transfer of the image to coordinate 

 paper, and also made possible careful comparison of gonopods with 

 previous illustrations. 



Extreme care was taken to orient the gonopods into a uniform posi- 

 tion for drawing, so that fictitious differences in appearance arising 

 from different aspects might be kept to a minimum. Failure to take 



