4 PROCEEDINGS OF THE NATIONAL MUSEUM vol. loe 



referable to the genus Sigmoria, as will be shown in a later paper of 

 this series. 



Fontaria pela was described bj^ Chamberlin (1918) from material 

 collected at Biirbank, Tenn. The original description did not contain 

 drawings of the gonopods, and the species, more or less unidentifiable, 

 dropped into obscurity for the next 30 years. In 1947, Chamberlin 

 described another new species as Dixioria dentifer, the type locality 

 of which is Cranberry, N. C. Less than two years later, in February 

 1949, 1 examined the type of Fontaria pela at the Museum of Compara- 

 tive Zoology and discovered that pela and dentifer are names based 

 upon the same species. Dixioria, therefore, becomes the proper name 

 for Fontaria pela as well as for my Deltotaria coronata. Although 

 there are considerable differences between the original drawings of the 

 gonopods of coronata and dentifer, I believe that the illustrations in 

 this paper will establish that the two are congeneric. The discovery 

 of intermediate forms also serves to corroborate this relationship. 



Taxonomic Characters 



The structural peculiarities which characterize the genus Dixioria 

 are fairly numerous and distinctive. The most obvious is the color 

 pattern, there being no other genera in the eastern United States in 

 which the dorsum is black with the caudolateral half of the paranota, 

 tip of the telson, and anterior edge of the coUum bright yellow. Be- 

 cause of this peculiarity, females as well as males can be placed into 

 Dixioria with confidence. However, since the pattern is identical in 

 all of the known forms, it is of no utility in separating species. 



Another generically diagnostic character is the configuration of the 

 paranota, of which both anterior and posterior corners are broadly 

 rounded on all except the last few segments. Among other xysto- 

 desmids of eastern North America, this feature is duplicated only in 

 some forms of Brachoria, all of which are considerably wider in pro- 

 portion to their length than of the relatively slender species of Dixioria. 



The gonopods of the male sex, while varying considerably in small 

 details, preserve an over-all similarity throughout the genus and are 

 distinctive from those of other known genera. The prefemoral process 

 is always present and conspicuous, in the form of a wedge-shaped, 

 usually slender, upright peg. The telopodite blade is very slender 

 and unmodified except at its distal end, forming an even cm-ve similar 

 to that found in the genus Apheloria. Distally the telopodite is 

 enlarged and provided with one or two subterminal processes of vari- 

 able size but usually thin and laminate in shape. None of these serves 

 as a solenomerite, as the seminal groove continues on to the tip of the 

 telopodite proper. 



