NEW MALI.Ol'HAGA. 117 



Upon the prothorax, iiiifl often excavated behind to 

 receive the latter. In Mcnupon /tersiijnatum , as shown 

 by transverse sections (plate xii), the liead is very Hat 

 and comparatively wide. Tlie side walls are very far 

 from being perpendicular, and are scarcely distinguish- 

 able from the dorsal walls. They meet the floor of the 

 cranium at a sharj) angle. Tiie top of the head is fiat 

 in front, somewhat concave behind. The protiiorax is 

 triangular in cross-section, having one angle median 

 and ventral. The terguni is a little rounded. The 

 mesothorax is more convex above and flatter beneatii. 

 The lateral edges are sharp and project over the bases 

 of the legs. The metathorax is wider Init otherwise 

 similar to the mesothorax except in length. In the 

 females of some species the abdomen is little or not 

 at all flattened. 



The body-wall of most species is well chitinized. In 

 the abdomen the chitin is deposited in several areas 

 around each segment (plate xv, figs. .3, 4, and 5. and 

 plate xvii, figs. 1-5). On the dorsal side is a wide con- 

 tinuous plate reaching on each side to a short distance 

 from the lateral margin of the segment. Likewise on 

 the ventral side is a similar chitinization, and the two 

 plates form respectively the tergum and sternum of the 

 segment. Laterally, between the outer ends of these, 

 are angular plates, one on each side, forming tlie lateral 

 walls or pleura of the segment. The four are sepa- 

 rated from one another by non-chit ini/.ed s})aces. The 

 intersegmental spaces are generally, especiallv on the 

 dorsum, thrown into S-shaped folds, so that the pos- 

 terior end of one segment overlaps the anterior end of 

 the one in front, in some cases the eliitinous tergum 

 or sternum of a segment occupies only a small part of 

 its lengtli. In some the chitin is mostly accumulated 



