THE CRAYFISH 



245 



in ventral view, is a broad, irregular ridge known as the molar 

 process. The basipodite and an endopodite of two joints 

 form a small three-jointed appendage or palp in front of the 

 coxopodite. The mandibles lie at the sides of the mouth. 

 Behind it come the limbs of the fourth pair, known as the 

 maxillules or first maxilla. Each of these consists of three 



Fig. 156. 



D F 



-The mouth appendages of the, left side of a crayfish. 



A, Third maxilliped ; B, second maxilliped ; C, first maxilliped ; D, maxilla (second 

 maxilla) ; E, maxillule (first maxilla) ; F, mandible in ven tral view ; G, the same 

 in dorsal view, showing molar process. 



bp. Basipodite; cp.. coxopodite; c?p., carpopodite ; dtp. dactylopodite ; en.. 

 endopodite; ep. t epipodite ; ex., exopodite ; gill ; isp., ischiopodite ; mrp., 

 meropodite ; pr.. protopodite ; prp. t propodite ; sb., setobranch or tuft of coxo- 

 poditic setse ; 1-5, joints of endopodite. 



thin plates joined to a small basal piece. One plate is an 

 expansion of the coxopodite, 1 the second represents the basi- 

 podite, and the third the endopodite. The fifth limb is the 

 maxilla (or second maxilla). It is a flat structure, deeply cleft 

 into several parts. The protopodite bears two thin lobes 

 directed towards the middle line of the body and each in 

 turn divided into two. 2 The endopodite is a narrow 



1 See note 2 to p. 244. 



2 The first double lobe probably represents the precoxa and 

 coxopodite ; the two parts of the second lobe probably belong to the 

 basipodite. 



