THE AMPHIPODA 



229 



antennae have almost a pediform character, the segments of the 

 peduncle being long and stout and the flagellum reduced, as in 

 the Amphithoidae and allied families and conspicuously in the 

 Corophiidae. 



The mandibles have usually the typical Peracaridan structure 

 with molar process, serrated incisor process, lacinia mobilis on the 

 left mandible or on both, a row of spines, and a palp of three 

 segments, but any of these parts may be modified or absent. The 

 palp, in particular, may be present or absent in genera otherwise 

 very closely related. 



The maxillulae (Fig. 137, A) are remarkable in that they 

 commonly exceed the maxillae in size and complexity of structure. 

 Two endites are present, springing, according to Hansen's inter- 

 pretation, from the first and third segments, and the fourth and 



i. 



FIG. 137. 



A, maxillula, B, maxilla, C, maxillipeds, of Socarntw bitlenticulatus (Gamnmridea). The 

 distal segments of the left maxilliped are omitted. 1-7, segments of the appendages; H-Z3, 

 endites of the respective segments. (After Hansen.) 



fifth segments form a " palp " which is turned forwards and inwards, 

 resembling in appearance, and no doubt also in function, a third 

 endite. The maj:illae (Fig. 137, B) are small in size and simple 

 in form, consisting mainly of two plates which, according to Hansen, 

 are the endites of the second and third segments. The lower 

 Up may attain to greater complexity than in most other divisions 

 of the Malacostraca and its modifications are of some systematic 

 importance. The two main lobes (paragnatha) of which it else- 

 where consists are in many cases supplemented by a pair of 

 accessory lobes lying between them, while the main lobes them- 

 selves may be produced at the outer corners or each divided by 

 incision into two as in the Amphithoidae. 



The first thoracic appendages or mtixillipeds (Fig. 137, C) are 

 always coalesced at the base, the coxopodites fusing to form an 

 unpaired plate. The basipodite is produced into an endite, usually 

 referred to as the " inner plate " (/ 2 ), which may be armed with 

 teeth, spines, or setae, but does not carry coupling -hooks. The 



