ISOPODS OF NORTH AMERICA. 



509 



tuberculate, the first two pairs being somewhat larger than the last 

 two pairs. The outer branches of the first four pairs and the fifth 

 pair of pleopoda consist of narrow, elongated appendages crenulated 

 on their outer margins and thickly tuberculate. The appendages of 



the sixth abdominal segment, the uropoda, are a pair of simple, cylin- 

 drical, elongated lobes, recurved at their extremities, and not reach- 

 ing beyond- the mass of epimeral appendages. 



The incubatory pouch is formed of five pairs of lamellae, five issuing 

 from one side and five from the other. The first pair are much smaller 

 than the others, and are entirely concealed by the second pair. 



The seven pairs of legs are all similar, and terminate in a prehensile 



