MILLIPEDS — ^HOFFMAN 215 



Distribution: P. c. retrorsus seems to be endemic to the middle 

 portion of the Tennessee Valley, ranging from the vicinity of Knox- 

 ville south into adjacent parts of Georgia and northern Alabama. 

 Specimens from the following localities have been examined : 



Tennessee. Knox County: Knoxville, 1 cf, C. N. Ainslie (MCZ, holotype). 



Alabama. DeKalb County: Mentone, 1 d^, August 1952, Lindsey S. Olive 

 (RLH). 



Georgia. No precise locality, but inferentially from the extreme northwestern 

 corner, 1 ? , Apr. 1, 1950, B. D. Valentine (RLH). 



Pachydesmus crassicutis adsinicolus, new subspecies 



Figures 10,c, 11, c 



Type specimen: Male holotype (USNM 2273) from Mobile, 

 Mobile County, Ala., collected Mar. 29, 1948, by William R. M. 

 Mason. 



Diagnosis: One of the smaller members of the laticollis phratry, 

 judging from the dimension of the single known specimen. It is 

 certainly closest to retrorsus, differing chiefly in the shape of the sec- 

 ondary tibiotarsus. In adsinicolus this structure is quite slender and 

 nearly parallel to the primary branch, the two converging distally. 

 In retrorsus the terminal elements of the secondary tibiotarsus are 

 strongly unequal in size and both are directed distad, whereas in 

 adsinicolus the terminal tip is bent mesiad and proximad. The 

 holotype, which is 69 mm. in length and 14.5 mm. in width, agi-ees in 

 nearly every particular with specimens of retrorsus. 



Distribution: Known only from the type locality. This form is 

 of considerable interest in emphasizing the curious north-south 

 distributional pattern of the laticollis phratry. The subspecific name 

 is given in reference to the habitat of the form near Mobile Bay. 



Relationships 



Generic relationships: The generic affinities of Pachydesmus are 

 not as obvious as have been surmised by previous investigators. 

 The superficial similarity of the gonopods to those of the species of 

 Harpaphe misled both Attems and Verhoeft' to combine the two genera, 

 despite a marked structm*al dissimilarity in other respects. Actually, 

 Harpaphe is a member of the Bhysodesmus-Boraria complex, it being 

 difficult to separate females of Harpaphe from those of Boraria 

 Carolina except by locality. The gonopods in Harpaphe are distinctly 

 diminutive, as is also the gonopod aperture, and I assume that the 

 secondary tibiotarsal process of Harpaphe must be the result of inde- 

 pendent convergent evolution. 



Attems (1938, p. 151) stated that the genera Takakuwaia {—Xysto- 

 desmus), Bhysodesmus, and Pachydesmus are very closely related but 



