254 THE APODID/E part u 



beyond the abilities of the writer to attempt to carry 

 this out in detail. 



In arranging the Crustacean groups, we propose 

 to ignore the usual division into Entomostraca and 

 Malacostraca. The Entomostraca we take to mean 

 all those groups which do not clearly belong to the 

 natural group of the Malacostraca. We therefore 

 prefer to divide the class into Phyllopoda, Malacos- 

 traca, Copepoda, Cirripedia, and Ostracoda. From 

 what follows it will be seen that we divide these five 

 into three groups, the first consisting of the Phyllo- 

 poda and Malacostraca ; the second, of the Copepoda 

 and Cirripedia ; and the third of the Ostracoda. We 

 believe that the first group is derived from the 

 Apodid^, the second from a larval Apus, and the 

 third, at least partly, from a Trilobite. This group- 

 ing, however, requires considerable investigation 

 before it can be definitely accepted. We leave it to 

 others who have made the different groups of the 

 Crustacea their special field of research to carry it 

 out in detail. We confine ourselves here to giving a 

 diagram representing the way we propose to construct 

 a natural order of the Crustacea based upon our 

 theory. We can, unfortunately, offer but little in 

 the shape of proof of this new classification, and 

 must content ourselves with appending a few discon- 

 nected notes on the different groups, which tend to 

 support our views. 



Taking the groups in the order in. which they 

 occur in the diagram from left to right, we may at 

 once dispose of the Eurypteridce and the Xiphosuridse, 



