THYSANURA 



407 



above high-tide mark along the sea shore and estuaries, are common 

 examples. In M«f:Mw (Figs. 303, 287) interesting features are presented 

 by the well-developed superlinguae and the jointed mandibles both of 

 which are primitive characters. The superlinguae in Machilis are paired 



Fig. 302. Lepisma saccharina. 

 From Imms, after Lubbock. 



Fig. 303. Machilis (Petrobius) maritimus. 

 From Imms, after Lubbock. 



Structures attached to the hypopharynx and possess inner and outer 

 lobes and a palp-like process. This superficial resemblance to maxillae 

 gave considerable weight to the view that an additional head segment 



