The Chonaphini 121 



sympatric representatives of the Apheloriini and Rhysodesmini. 

 Combining body form with color pattern allows one to unfailingly 

 recognize S. placidus in the field. 



Aside from the size and degree of decline of the paranota, there 

 are few noteworthy aspects of the somatic details. The epiproct of T. 

 levii displays a narrow constriction (see Causey 1954«, fig. 2), whereas 

 those of the other taxa are smoothly subtriangular. Low lateral ridges 

 subtend the anterior coxae, and the glaborous pregonopodal sterna, 

 depressed on segment 6 and the caudal half of segment 5 to accommodate 

 the gonopodal telopodites, generally lack modifications aside from 

 long, diverging projections on the 4th sternite of S. placidus (Fig. 

 27). The postgonopodal sterna also are glabrous and unmodified, with 

 only shallow transverse grooves between the leg pairs and gently 

 curved caudal margins. The pregonopodal coxae oi Metaxycheir prolata 

 are swollen with slight anteriorly directed lobes but are unmodified 

 in other species. Prefemoral spines are present in all species, but only 

 on postgonopodal legs and often only in the caudal half of the body. 



Aperture — The aperture in the Chonaphini usually extends caudad 

 to at least a small degree in the midline. The only exceptions are 

 T. levii and Chonaphe evexa, which resemble other northwestern 

 xystodesmids in lacking even a trace of a caudal extension (Figs. 15, 

 46). This feature of the aperture is particularly noticeable in C. armata 

 and S. placidus (Figs. 2, 28), which have long, broad extensions, and 

 is another trait that distinguishes the latter from sympatric representa- 

 tives of other eastern tribes. Within these extensions is a sclerotized 

 ledge or shelf that I believe represents the sternum between the 9th 

 legs. Thus, it is really only the elevated caudal margin that extends or 

 "peels" caudad, analogous to "peeling" the backing off a gummed 

 label; the opening itself is ovoid to elliptical. However, in C. armata 

 and S. placidus, the extensions are so obvious as to appear a functional 

 part of the opening even though they are not. 



Gonopods — As stated previously, the Chonaphini is unique in 

 that the prefemoral processes are highly variable and possess most 

 taxonomically important features, whereas the acropodites are simple 

 and with little taxonomic utility, as opposed to the reverse in all 

 other xystodesmid tribes. All genera and most species can be diagnosed 

 from aspects of the prefemoral process, which is the dominant gono- 

 podal feature, overshadowing the acropodite in most forms. The arrange- 

 ments of the telopodal elements relative to each other are also important, 

 the prefemoral process and acropodite being subparallel in Semionellus 

 and Montaphe, and not parallel in the other genera. It is this shared 



