314 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 117 



stricta the receptacle is set with a number of prominent macrosetae 

 that are absent from the structure in B. media and B. deturkiana. 



There is also some difference in shape of the valves. In some genera 

 they are rather broad and prominently corrugate and enclose a flat- 

 tened, transversely striate intervalvular area. In most of the 

 Rhysodesmini the valves tend to be compressed and closely applied 

 to each other; usually one is distinctly larger than the other. In- 

 ternally the valves contain one or more seminal receptacles of variable 

 size and shape. In Boraria there appear to be two such structures 

 (fig. 5) ; in Gyalostethus, one only. So far, I have not studied the 

 condition in other xystodesmid genera, but such a study should be 

 made and probably would be entirely rewarding. 



Stigmata. — Insofar as I have been able to determine, the open- 

 ings of the tracheal system in the Diplopoda have never been consid- 

 ered for their possible utility in classification. During the past few 

 years, I have been noting the size, shape, and position of the stigmata 

 and find they offer excellent generic and familial characters that cor- 

 relate closely with those of the genitalia and other traditional diag- 

 nostic structures. In the Xystodesmidae the stigmata tend to be 

 essentially similar among related genera, usually subequal in size, 

 obverse pyriform in shape, and located just in front of (often upon) 

 the dorsal coxal condyle. In some cases the stigmata may be located 

 upon slight elevations or the dorsal edges may be slightly flared. In 

 Gyalostethus the anterior stigmata are distinctly larger than the 

 posterior, an unusual condition in the family and one which warrants 

 special recognition. 



Taking all of the preceding matters into account, I think the point 

 is sufBciently made that G. monticolens is not congeneric with the 

 three species B. stricta, B. media, and B. deturkiana. We may place 

 it in a monotypic new genus, separable from Boraria by the characters 

 cited in the preceding section and in the generic diagnoses that 

 follow. Some of the more conspicious characters may be cited in 

 the following couplet: 



1. Sterna of metazonites unmodified; sides of segments without a longitudinal 

 ridge above coxal sockets; pretarsi about Yz as long as tarsi, not concealed 

 by long tarsal setae; stigmata not strikingly unequal in size; posterior 

 corners of paranota of only the caudalmost segments produced; distal end 



of gonotelopodite simple, laminate Boraria, p. 315 



Sterna of metazonites unusually broad and depressed, saucer-like; segments 

 3-15 with a distinct longitudinal ridge just above coxal sockets; pretarsi 

 very short, largely concealed by long, slender distal tarsal setae (fig. 23); 

 anterior stigmata about 3 times as large as posterior; caudolateral corners 

 of paranota of segments 6-19 acutely produced; distal end of gonotelopodite 

 expanded, cupulate, the edges finely laciniate .... Gyalostethus, p, 338 



