MILLIPEDS — HOFFMAN 189 



entire shape is quite different from that of the other three subspecies 

 enumerated. 



Genus Pachydesmus Cook 



Pachydesmus Cook, 1895, p. 5.— Pocock, 1909, p. 188. — Attems, 1938, p. 153. — 

 Chamberlin and Hoffman, 1958, p. 42. 



Type species: Polydesmus crassicutis Wood 1864, b}^ original 

 designation. 



Diagnosis: A genus of moderate to large, rather bulky xysto- 

 desmids of variable structure with the following characteristics: 



Head smooth and polished, the vertigial groove terminating ante- 

 riorly in a small but distinct interantennal depression; two frontal, two 

 subantennal, and four supra-antennal setae present; antennae slender 

 and moderately long, extending caudad to middle of 3d tergite, with 

 four sensory cones; genae somewhat swollen and with distinct median 

 grooves. 



Paranota moderately developed, slightly less than a third as wide as 

 diameter of body cavity, continuing or but slightly interrupting slope 

 of dorsum. Pores normal in distribution, opening on the dorsal side 

 of the peritremata. Tergites very finely coriaceous, often with several 

 transverse rows of very tiny setiferous tubercules. 



Sterna smooth and completely glabrous, not produced at the bases 

 of legs, podosterna appreciably raised above level of prozonites. 

 Pleura finely granular, without ridges or clusters of tubercules. No 

 processes or knobs between 3d and 6th legpairs of the male. 



Coxae of gonopods large, connected only by sclerotized membrane, 

 there being no zygomatic structure; each coxa with two elongate 

 macrosetae and a coxal apophysis of variable size above the origin of 

 the solenite. Prefemur elongated from a slightly globose base, 

 densely setose, with a moderately large, slender, weakly chitinized pre- 

 femoral process which is bent at an obtuse angle at about its mid- 

 length. Acropodite of gonopod (coalesced femur and tibiotarsus) a 

 thin, heavily sclerotized blade with distinct seminal groove and 

 distally bent at a right angle. A large secondary tibiotarsal branch 

 originates at the base of the telopodite, and is bent strongly distad, 

 subparallel to and usually as long as the main branch, often modified 

 distally with a subterminal spur of variable size and shape. 



Anterior edge of ventral ends of pleurotergites of the 3d segment in 

 females produced cephalomesiad into a large rounded elongate lobe 

 which partially extends in front of the coxae of the second pair of legs. 

 Immediately caudad to these lobes the pleurotergite is produced into a 

 rather high, thin, marginal flange. 



Cyphopods large and conspicuous, of the characteristic polydesmoid 

 form and not strikingly different from those of other xystodesmid 



455980—58 2 



