INTRODUCTION. 



In the present volume I propose to give an account of 2 anomalous 

 groups of Copepoda, viz., the Monstrilloida and the Notodelphyoida, the 

 systematic position of which has not been fully recognised by earlier authors. 

 In the more recent classification of the Copepoda proposed by Giesbrecht, and 

 now generally adopted by carcinologists, only the systematic rank of families 

 is alloted to these groups, and they are both, together with several other 

 heterogeneous families, comprised within the 2nd tribe of this suborder Podoplea, 

 to which the name Ampharthrandria is given. I have otherwise shown, that 

 the principles upon which Giesbrechts classification is founded do not at all 

 hold good in every case, and this is also proved in regard to the Copepoda 

 here in question. It may be that the name Ampharthrandria is appli- 

 cable to the Monstrilloida; but this is by no means the case with the 

 Notodelphyoida, this group comprising many forms with the anterior antennae 

 quite alike in the 2 sexes. Moreover, the genus Thaumatopsyllus among the 

 Monstrilloida differs conspicuously even in the principal character by which 

 the 2 suborders Gymnoplea and Podoplea are distinguished by Giesbrecht, 

 viz., the mutual relation between the anterior and posterior divisions of the 

 body. The many essential characters distinguishing the 2 groups here treated 

 of, both from each other and from the other known Copepoda, have led me 

 to the conclusion, that they ought to be raised to the rank of distinct divisions, 

 to be again subdivided into real families. The relation of these divisions to 

 other known groups of Copepoda is somewhat obscure, though in some instances 

 a tendency towards the Cyclopoid type is unmistakable. On the other hand, 

 by an extreme degradation of the whole body and its appendages, some forms 

 belonging to the Notodelphyoida acquire an appearance, strongly recalling that 

 of the Lernceoida. All the forms here in question are in some measure 

 parasitic in habits. But the parasitisme is of a very different kind in the 



1 Crustacea. 



