292 Annals Entomological Society of America [Vol. XV, 



ventrally; the inner pleural margins are thickened; to their posterior 

 angles are attached flattened lobes, twisted perpendicularly, which 

 overlap each other; the anterior angles are produced into strongly 

 chitinised hooks bent dorsally (Fig. 25, B). The upper ends of the 

 hooks are connected by a tough membrane, stretched perpendicularly, 

 in the middle of which are found the relics of the atrophied sternite 

 of the second pair of legs {P2). These relics consist of a subreniform, 

 irregularly chitinised, transverse plate, with no definite outline, showing 

 traces of stigmata and of tracheal stalks; the limbs have disappeared 

 altogether. 



The space left between the membrane and the ventral lobes is 

 filled with vulvae. The vestibulum could not be observed, being 

 probably shallow. The vulvae stand side by side, connected by soft 

 membrane, with the operculum facing cephalad. The general appear- 

 ance of a vulva is that of a truncate spindle or of a tiny cask. The 

 operculum is flattened, oval in outline, and bears macrochaetse disposed 

 in four longitudinal rows, two lateral and two paramedian rows, the 

 latter converging proximally. The valves {iv, Fig. 26), are almond- 

 shaped, with a median row of bristles, and stand erect. The central 

 part of the mound, i. e., the horseshoe plate and the ridge framed by 

 its branches, are strictly comparable to the mound of tiganus, which 

 would have undergone a caudal rotation of 45°, causing the ridge to 

 face fully backwards (Fig. 27). Ridge oval. The slit divides the 

 summit of the mound and part of the ridge into fairly symmetrical 

 halves. The apodema is short, but ends in an extremely long, slightly 

 sinuous, tubular diverticulum. 



Paraiulus immaculatus Wood, 1864. 



(Fig. 28-34). 



9. Length 36 mm.; diameter 2.65 mm.; 51 segments, of which 2 apodous; 

 92 pairs of legs. — Adult. 



9. Length 31 mm.; diameter 2.10 mm.; 51 segments, of which 2 apodous; 

 92 pairs of legs. — Adult. 



Interocular sulcus not impressed. Antenna moderately long, 

 not exceeding the fourth segment; comparative measures of joints as 

 below: 



1st joint, length 0.160 mm. 



2d joint, length . 544 mm. 



3d joint, length . 480 mm. 



4th joint, length 0.448 mm. 



5th joint, length 0.416 mm. 



6th joint, length 0.352 mm. 



7th-8th joint, length 0.128 mm. 



diameter 0.208 mm. 



diameter 0.224 mm. 



Total length 2 . 528 mm. 



Mandibular cardo (Fig. 30) about equal to three-fourths of the 

 stipe, the latter being longer than usual, and rounded anteriorly. 

 Mandibula furnished with 8 to 9 pectinate lamellae. Promentum 



