290 Annals Entomological Society of America [Vol. XV, 



Genus Paraiulus Humbert & Saussure, 1869. 



Paraiulus tiganus Chamberlin, 1910. 



(Figs. II and 10-21). 



9. Length 37 mm.; diameter 2.44 mm.; 56 segment?, of which 2 apodous; 

 102 pairs of legs. — Adult. 



9. Length (?); diameter 2.48 mm.; 55 segments, of which 2 apodous; 100 

 pairs of legs. — Adult. 



9. Length (?); diameter 2.44 mm.; 55 segments, of which 2 apodous; 100 

 pairs of legs. — Adult. 



9. Length 39 mm.; diameter 2.38 mm.; 54 segments, of which 2 apodous; 

 98 pairs of legs. — Adult. 



9 . Length 29 mm.; diameter 2.05 mm.; 52 segments, of which 2 apodous; 94 

 pairs of legs.* — Immature. 



Adult Female. — Interocular sulcus deeply impressed. Antennas 

 moderately elongate; comparative measures of joints as follows: 



1st joint, length 0. 192 mm 



2d joint, length 0.608 mm. 



3rd joint, length 0.544 mm. 



4th joint, length 0.512 mm. 



5th joint, length . 480 mm. 



6th joint, length . 448 mm. 



7th-8th joint, length 0.192 mm. 



diameter . 224 mm. 



diameter 0.240 mm. 



diameter 0.240 mm. 



diameter 0.288 mm. 



diameter . 272 mm. 



Total length 2.976 mm.. 



Mandibular cardo (Fig. 13) equal to two-thirds of the stipe. Mandib- 

 ular stipe short and broad (ratio: 1. 6 x b. 5), rounded anteriorly. 

 Promentum entirely dividing the laminae linguales; the latter bear six 

 setffi in a longitudinal row, besides the usual premarginal bristle. 



vSecond and third segments (Figs. 10, 11) conspicuously swollen. 

 Profile of second segment angular; ventral ridges low (Fig. 13), almost 

 regularly curved; dimples oval, broader than long; ventral lobes large, 

 over-lapping each other. Third segment tapering ventrally, with 

 profile scarcely convex. Anterior aspect as in Fig. 13, B. 



Legs of second pair much reduced (Fig. 14). The sternite {S) is a 

 short but broad stripe, with posterior margin straight and outer angles 

 unusually produced. Tracheal ■ stalks more or less developed. The 

 six joints of the limbs are preserved, all except the two distal joints 

 being shorter than broad; first joint almost completely fused with the 

 sternal plate; last joint oval, tipped with a spine-like claw. 



Vulvar vestibulum moderately deep, with a wide aperture not 

 constricted by symmetrical folds, fastened to the duplicatures of the 

 third segment and to the anterior margin of the fourth. The vulvae 

 sit at the bottom of the vestibultmi side by side, the operculum facing 

 externally and somewhat forwards. 



The mound is a very low, semi-cylindrical body, the walls of which 

 represent the horseshoe plate probably fused with the valves (Figs. 

 15, 18). The inner region of the wall is more raised and more convex 

 than the outer, causing the mound to be asymmetrical, with the ridge 



* The last leg-bearing segment has but a single pair of limbs. 



