1922] Brolemann: Female Paraiulids 283 



to readers of the following descriptions, to draw an elementary 

 sketch of . a vulva and to make them acquainted with the 

 terms which have been applied to the different parts of these 

 puzzling organs. 



The two branches of the oviduct are known to end behind 

 the legs of the second pair and to be capped with vulvae. In 

 most of the Diplopod groups {Colobognatha and Oniscomorpha 

 excepted), the vulvae are concealed in a deep depression of 

 the intersegmental membrane, which will be known as the 

 vulvar ' ' vestibulum. ' ' In some cases the vulvae stand side 

 by side in the vestibulum, while in some others they are sunk 

 into independent, lateral invaginations of the vestibulum, 

 apart from each other, (Fig. 3). The position of the vulvae is 

 therefore very different, according to the various cases; but 

 whatever it may be, in order to make things obvious, a vulva 

 is always considered isolated and standing with • its free end 

 upwards (as represented in Figs. 26 and 27, Paraiulus penn- 

 sylvanicus, for instance). 



In condition of rest, the terminal region of the oviduct 

 may be compared to a funnel which has been pressed flat, 

 causing the aperture to be linear and perpendicular to the 

 main axis of the body. Immediately behind the aperture 

 the neighboring surface is raised into a more or less projecting 

 and rounded, always very conspicuous jutting, called the 

 "mound." Its lateral slopes are protected by chitinised plates, 

 reminding one of the shells of a Lamellibranch, and con- 

 sequently termed the (inner and outer) "valves," (iv, Fig. 26). 

 An apical space, the "ridge," (r, Fig. 27), is left between the 

 valves, made of colorless chitine, below which is to be seen a 

 longitudinal chitinous, gutter-shaped thickening, the"apodema," 

 (a), extending perpendicularly to the aperture of the oviduct. 

 The apodematic gutter communicates with the exterior by 

 means of a longitudinal "slit," which divides the ridge into 

 more or less regular halves. 



In some cases the posterior ends of the valves remain free, 

 the ridge being open backwards; in the case of lulids, the 

 valves are generally connected by, and often fused with a 

 posterior-median plate, the anterior margin of which is emar- 

 ginate and thickened in shape of a horse-shoe ("horse-shoe 

 plate"). The latter bounds the ridge caudad, {h, Fig. 27). 



