ISOFODS OF NOETH AMERICA. 



509 



tiibeiculate, the first two pairs being soniewiiat larger than the last 

 two pairs. The outer branches of the tirst 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, elon<^;-ated lobes, recurv^ed at their extremities, and not reach- 

 ing beyond the mass of epimeral appendages. 



The incubatory pouch is foi'med of live pairs of lamellae, live 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 



