HANSEN AND SÖRENSEN, THE TARTARIDES. 15 



and it is much elongate in front so that it, seen from above 

 (Pl. 5., fig. 3 k), is continued forwards as a low broad cone 

 beneath the eleventh and the posterior part of the tenth 

 tergite. In the male Schizomus siamensis n. sp. the twelfth 

 segment is posteriorly produced into a long, somewhat com- 

 pressed process protruding above the proximal part of the 

 flagellum (PL 5., fig. 2 g), while the front part of the seg- 

 ment is produced forwards as in T. p^ocerus. In Schizo- 

 mus crassicaudatus Cambr. there is scarcely any perceptible 

 difference between these segments in the male and in the 

 female; in Schizomus Simonis the posterior part of abdomen 

 seems always to be considerably less telescoped in the male 

 t han in the female. 



Flagellum differs very much in the two tribes. In Oxo- 

 poei it is always long with many movable joints (except 

 in exceedingly young, newly hatched specimens); probably 

 always several of the joints have one yellowish »spöt» below. 

 In Tartarides flagellum is always short, without spöts on the 

 lower side, but it differs extremely in the two sexes. In the 

 females it is subcylindrical and divided into three or four 

 joints by articulations which are so feebly developed that 

 they scarcely allow movability; it is adorned with several 

 setse arranged almost in the same way in various species. In 

 adult males flagellum is always unjointed, thickened and 

 more strongly chitinized than in the female, of ten brown, 

 but differs exceedingly in shape in various species and affords 

 excellent specific characters. We think it sufficient here to 

 refer to the figures of the flagellum of the eight males de- 

 scribed in the sequel; it may be added that the flagellum 

 always ought to be figured as thoroughly as possible both 

 from the side and from above. In immature males it is so- 

 mewhat thickened (Pl. 2., fig. 2 h) but otherwise more like 

 that in the female. 



The dorsal surface of abdomen has two longitudinal rows 

 of rather short setse, which are simple and thin in most spe- 

 cies, subclavate and very conspicuous in Trithyreus claviger 

 n. sp.; at least in this species several segments have two 

 additional subclavate setse placed more distant from the me- 

 sial line. The lower surface of abdomen is more hairy, on 

 the posterior segments adorned with elongate setse; several 

 of these are (Pl. 3., fig. Ig) even very long, cylindrical, with 

 the apex bifid. 



