XI 



PHYLUM ARTHROPOD. V 



573 



1RX, 



are a pair of stout mn-niliiilcs (Fig. 454, md., and 455, man.}, 

 which work horizon- 

 tally like those of the 

 ( Ynyfish ; their inner 

 edges are divided 

 into a number of 

 teeth. Behind the 

 mandibles are a more 

 flexible pair of jaws 

 the first pair of 



'Yl'i ft / y ) ''i ///V' l'557'J* 05? ft i' 1 



Each maxilla exhibits 

 a structure compar- 

 able to the funda- 

 mental type of the 

 appendages of the 

 Crayfish ; a basal part 

 or protopodite, consist- 

 ing of two segments 

 (podomeres), support- 

 ing an internal ramus 

 or endopodite, and an 

 external ramus or 

 ex( ,j>oditc. The former 

 consists of two parts : 

 an inner, pointed, hard 

 Made - - the lacinia 

 (mi}, and an outer, 

 softer, more elongated the galca (me}. The exopodite forms a 

 palp, the maxillary palp (pm.), consisting of five podomeres. Behind 



these are the second maxillae, which 

 are reducible to the same type, but 

 which have their two basal seg- 

 ments (those of the protopodites) 

 united together in the middle line, 

 to form two median sclerites, 

 known respectively as mentum (m.) 

 and submcntum(sm}, so that the two 

 appendages form a sort of lower lip 

 called the labium. The endopo- 

 dites taken together constitute 

 what is termed the ligula ; each 

 is divided into two parts like the 

 endopodite of the first maxillae. 

 The exopodites form three-jointed 

 palps, the l(il>inl palps (pi}. 



The neck, or narrow region 



Fin. 4")4. Mouth parts of the Cockroach ; Hi,-, labrum ; 

 mil. mandible ; mx 1 . anterior pair of maxillse ; //*. mentiini ; 

 me. ainl mi. miter and inner divisions of the sermnl 

 pair of maxilla;; j>l. labM palp.; JHH. maxillary palp; 

 xt. stipes; sm. submentum. -(From Langs Comparative 

 Anatomy.) 



gen. 



cerv 



;. 4V,. Periplaneta americana. 



Lateral view of the head and its ap- 



pondages. n>. one of the cervical 



sclerites; ey. eye; gen. gena ; man. 

 inundible; max*., first pair of max- 

 /((.--. second pair f maxilla 



