SEA-EIS11EIIIES LA1J0 



297 

 ified exoskeleton, 



dian portion — the 

 continued into two 

 the median ventral 



dorsal side there is thick and highly 

 but the ventral wall is membranous. 

 The dorsal wall consists of a 

 tergum (text fig. 1, t.) — which is 

 broad lateral portions — the pleura. 

 wall is known as the sternum, and from each of the outer 

 portions of the sternum arises in appendage. Between 

 the point of attachment of eacn appendage and the 

 pleuron the ventral wall is known as the epimeron. 



t 



Fig. 1. — Diagrammatic section through female abdomen. 



t.= tergum. 

 p.= pleuron. 

 s. = sternum. 

 e.= epimeron. 



e.m. — extensor muscles of abdomen. 

 f.m.— flexor muscles of abdomen. 



m.a.= muscles of abdominal 



appendage. 

 li.g. =hind gut. 

 _pr.=protopodite. 

 ex. = exopodite. 

 en. =endopodite. 



The segment is connected with the two neighbouring 

 segments by a thin uncalcified part of the exoskeleton — 

 the arthrodial membrane. This allows of free movement 

 between the segments. Each segment articulates with 

 the one in front by means of a pair of hinges placed at 

 the outer and anterior part of the pleuron at each side. 



The appendages will be described in detail later. 



Cephalothorax. 



1. Carapace. 



The terga and pleura of the cephalothorax are fused 

 to form the large Carapace. This is a broad shield the 

 width of which is about 1\ times as great as the length. 



