ENTOGNATHY IN APTERYGOTES — TUXEN 



393 



so-called tentorium, is present, not V-shaped, but Y-shaped, the lateral 

 branches being coalesced to a large extent. From this fulcrum 

 branches are given off to the clypeus and two short dorsal arms at 

 the middle. A hypopharynx is absent. The mandibles extend back- 

 ward to a little behind the roots of the maxillae, but as they are very 

 movable within the head their exact position is not easily defined. 



-~-\-cd 



Fig. 9. — Onychiurus annatus Tullb. Head with maxillae and fulcrum, dorsal, 

 mandible omitted. Maxillae dotted. 



The shape of the gnathal pouches is not easily seen, but from 

 figure 14 it appears that the maxillary pouch is very broad anteriorly 

 where it contains the palpus. At this place it is continuous with the 

 mandibulary pouch, but in the hind part of the head no such connec- 

 tion seems to be present. Cross sections may decide. 



The labium is a small triangular piece as in Collembola with distinct 

 palpi, but also with structures parallel to what Hoffmann (1908, 



