20 



On the dorsal side of the abdomen the terga are 

 separated from the pleura by two longitudinal grooves. 

 Ventrally the median portion is covered by a thin 

 uncalcified cuticle and the outline of the hind-gut is 

 clearly seen. 



The hind-gut opens on the ventral side of the telson 

 at the anus. 



Only the first somite requires any special comment. 

 The upper side of this somite is prolonged forward as a 

 thin triangular flap, the apex of which points anteriorly. 

 This triangular portion is covered by the carapace, only a 

 narrow region at the posterior end of the somite being 

 exposed. All around the anterior edge of this somite is a 

 thin membrane which is continuous with the posterior 

 region of the cephalothorax. 



The first two somites are hollowed out laterally to 

 provide free movement for the last pair of thoracic legs. 



Male (PL I, fig. 3). 



When lying in position the abdomen extends slightly 

 in front of the middle of the fourth thoracic sternum. 

 It is slightly shorter than the female abdomen and much 

 narrower. As in the latter, the sides of the first two 

 somites (and also part of the third) are hollowed out and 

 pass round the inner sides of the last pair of thoracic 

 appendages. 



The first somite has the same arrangement. as in the 

 female. The anterior part of the dorsal side is triangular 

 and is covered by the carapace. 



The third, fourth and fifth somites are fused together 

 so that there is absolutely no movement between them. 

 The sutures marking their separation still persist. 



There are only two pairs of appendages which are 

 present on the first and second somites respectively. 



