950 The Paleozoic Allies of Nebalia. [December, 



they certainly do not belong; and thus, reasoning by exclusion, 

 they either belong to the group of which Nebalia is a type, or 

 they are members of a lost, extinct group. The natural conclu- 

 sion, in the light of our present knowledge, is, that they are 

 members of the group represented by the existing Nebalia. 



.v,. y.—Dithyrocaris neptuni Hall; telson and cercopoda, natural size, trom 



In order, then, to summarize our present knowledge of the liv- 

 ing Nebalia and its fossil allies, we will give what we regard as 

 the characters of the group, which may be regarded as provis- 

 ional, though perhaps of some present use. 



External diagnostic characters of the order Phfllocarida.—Body 



