LIGIA. 71 



this forms a true posterior lip. The maxillary excretory 

 organ opens at the base of the second maxilla. 



The seven segments of the thorax form the greater part 

 of the animal's body. They are convex on their anterior 

 margins and concave behind. The lateral portions form 

 large epimeral plates, obtusely acuminate, and directed 

 backwards. The segments slightly overlap, and the 

 uniting membrane, which is not impregnated with 

 calcareous salts, sinks into the hypodermal tissues. On 

 the ventral sides, where the epimera join the body, the 

 walking legs or pereiopods arise. The first three pairs 

 of pereiopods are approximately the same size, the last 

 four pairs gradually increase in size. The ventral wall 

 of the thorax is thin and transparent, and strengthened 

 by slightly curved transverse bars. On the ventral side 

 of the thorax of the female, the brood-pouch full of ova 

 is very conspicuous in the breeding season. It is formed 

 by lamellae which arise inside the origin of the five 

 anterior pairs of thoracic appendages and grow ventrally, 

 overlapping the adjacent lamellae distally and laterally. 

 The paired female genital apertures are situated on the 

 inside of the fifth pair of pereiopods. The male genital 

 products are ejected through a pair of styliform 

 appendages on the posterior border of the last thoracic 

 segment, immediately in front of the branchiae. 



The metasome or abdomen consists of five segments 

 and the telson, and is about a third of the entire" length 

 of the animal. The two anterior segments are narrow, 

 and do not reach the margins, but are lodged in the 

 concave posterior border of the seventh thoracic segment. 

 The three posterior segments have their lateral margins 

 produced into tooth-like backwardly projecting processes. 

 Five pairs of uropoda, which are of the nature of 

 branchiae, are borne on the ventral side of the abdomen. 



