7^ 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 85 



thoracic and abdominal styli will be discussed in the concluding part 

 of this Section, but in any case the term " coxite " should not be used 

 to designate the stylus-bearing plates, because the word can properly 

 mean only " a part of a coxa." Since the writer is inclined to believe 

 that the abdominal plates in question represent both the coxae and 

 the subcoxae of the thoracic appendages, they are here termed simply 

 the limb bases, or basal plates. 



The gonopods, or appendages of the genital segments, have the 

 same structure as the pregenital limbs in Thysanura, with the excep- 

 tions that they always lack eversible vesicles, and that typically each 

 bears a median genital process, or gonapophysis (fig, 31 B, Gon). 

 Two pairs of gonapophyses are regularly present in the females of 



-IXSty 



Fig. 33. — Genital and postgenital segments of Machilidae. 



A, Machilis variabilis, male, ventral plates of eighth abdominal segment, dor- 

 sal view, with small first gonapophyses (iGon). B, ventral plates of ninth seg- 

 ment of same, dorsal view, showing second pair of gonapophyses {2Gon) at 

 sides of median penis {Pen). C, Nesomachilis maoricus, male, posterior part of 

 abdomen, ventral view, showing absence of gonapophyses, and ventral structure 

 of eleventh segment, bearing paraprocts (Papt), caudal filament (cf), and cerci 

 (Cer). 



Thysanura, one pair borne by the gonopods of the eighth segment, the 

 other by the gonopods of the ninth segment. In the male, gonapophy- 

 ses are known to occur on the gonopods of the eighth segment only 

 in certain forms of Machilis (fig. 33 A, iGon) ; they are usually 

 present on the gonopods of the ninth segment (B, 2Gon), but they 

 may be absent from both genital segments (C). Each gonapophysis, 

 when present, arises from the median, basal angle of the free dorsal 

 surface of the stylus-bearing plate, and is provided with short muscles 

 (fig. 31 B, gnicls) arising within the supporting plate and inserted 

 on its base. 



Between the bases of the gonopods of the ninth segment in the male 

 is a short membranous penis (fig. 33 B, C, Pen), a tubular evagination 



