94 ESSENTIALS OF ZOOLOGY 



The appendages are : 



Head. Antennules, or Anterior or First Antennae. 

 Antennae, or Posterior or Second Antennae. 

 Mandibles. 

 1st Maxillae. 

 2nd do. 



Thorax. 1st Maxillipeds. 

 2nd do. 

 3rd do. 

 Pereiopoda, or Walking Legs five pairs, the 



first pair being the Chelae, or pincers. 

 Abdomen. Pleopoda, or Abdominal Appendages six 



pairs. 



The sixth pair of abdominal appendages are 

 called Uropoda. The last segment, the 

 telson, bears no appendages. 



The appendages typically consist of a basal portion or 

 peduncle (protopodite) bearing two rami (exopodite and 

 endopodite), but they are more or less modified according to 

 the position they occupy and the function they perform. 



The antennule consists of a three-jointed peduncle (proto- 

 podite) bearing two sub-equal flagella. The outer flagellum 

 (exopodite), is slightly thicker than the inner (endopodite). 

 The basal segment of the peduncle is longer than the other 

 two together ; the proximal part of this segment is expanded 

 and contains the auditory sac. The flagella function as tactile 

 and as olfactory organs. 



The antenna is made up of a two-jointed peduncle (proto- 

 podite) bearing a flattened antennal scale externally (exo- 

 podite) and the long feeler (endopodite). This latter consists 

 of three basal segments (peduncle of flagellum) and the long 

 flagellum, made up like the flagella of the antennules of a 

 large number of very short segments. The flagellum is tactile. 

 The first segment of the protopodite presents on its ventral 

 surface a prominent tubercle bearing the opening of the 

 antennal or green gland ; the second or distal segment is 

 produced externally into a process. 



The mandible, the first oral appendage, is very much 



