1 882.] The Palceozoic Allies of Nebaha. 95 1 



compressed ; consisting of twenty-one segments — five cephalic, 

 eight thoracic and eight abdominal. Carapace compressed, with, 

 no regular hinge, loosely attached to- the body by an adductor 

 muscle ; with a movable rostrum inserted in a depression in the 

 front edge, the carapace covering the basal joints of the abdomen. 

 One pair of stalked eyes ; no simple eyes. Two pairs of well- 

 developed, many-jointed, long, large antennae, the first pair bira- 

 mous, the second pair with a very long flagellum in the male. 

 Mandibles weak, with a remarkably long three-jointed palpus. 

 Two pairs of maxillae ; the first with a remarkably long, slender, 

 multiarticulate exopodite; second pair well developed, biramous ; 

 no maxillipedes ; eight pairs of biramous, broad, thin, respiratory, 

 thoracic feet, not adapted for walking; the exopodites divided 

 into a gill and flabellum ; four pairs of large and two pairs of 

 small abdominal swimming feet ; no appendages on the seventh 

 segment, the terminal one bearing two long caudal appendages 

 (cercopoda). No telson present in the living species ; well devel- 

 oped in the Ceratiocaridae. Young developed in a brood sac ; 

 development direct; no marked metamorphosis ; the young but 

 slightly differing from the adult. 



Remarks. — By the sum of the foregoing characters the Phyllo- 

 carida appear to be excluded from any other group of Neocari- 

 dan Crustacea. 



The differential characters separating them from the Decapods 

 or any other Malacostracous type, are : 



1. The loosely-attached carapace, the two halves connected by 

 an adductor muscle. 



2. The movable rostrum, loosely attached to the carapace. 



3- The very long and large mandibular palpus ; the long, slen- 

 der appendage of the first maxillae, and the very long biramous 

 maxilla. 



4- The absence of any maxillipedes. 



5- The eight pairs of pseudophyllopod thoracic feet, not adapted 

 for walking ; the animal swimming on its back. 



7- No zoea-formed larva. 



The differential characters from the Phyllopods are the fol- 

 lowing : 



1. Carapace not hinged ; a rostrum present. 



2. Two pairs of well-developed long and large multiarticulate 

 antennae; the hinder pair in the male longer than the first pair. 



