INTRODUCTION. 
1 he Cumacea form a sharply-defined and very peculiar group of Crustacea, 
the systematic position of which has been much debated among zoologists, most 
of the earlier authors referring them to the lower Decapods, whereas in recent 
time they have generally been placed close to the Isopoda. The fact is that they 
differ materially from both of these groups, and should thus more properly be consi¬ 
dered as constituting a distinct order, occupying its place between the great divisions 
Podophthalmia and EdriophthaImia . It is true, inded, as first shown by Dr. Dohrn, 
that the embryonal development of the Cumacea agrees very nearly with that of the 
Isopoda; but in all other respects these Crustacea exhibit, in my opinion, a much 
closer relationship to the Podophthalmia than to the Isopoda. Among the former, 
it is chiefly the Schizopoda with which the Cumacea have many features in com¬ 
mon, though the external appearance is certainly very different; and even 
those anatomical characters which have been specially adduced as proofs of 
the near relationship of the Cumacea with the cheliferous Isopoda, viz., the pre¬ 
sence of a reflexed palp on the anterior maxillse, and the peculiar development 
of the epipodite on the 1st pair of maxillipeds, may be found quite as distinct 
in some of the Schizopoda, e. g. Gnathophausici. In my opinion, therefore, 
the recent arrangement of the Cumacea as a sub-order of the Edriophthalmia can 
scarcely he supported. On the other hand, I consider that the differences from the 
Schizopoda are still great enough to forbid of the Cumacea being included in the 
great division Podophthalmia. 
Our knowledge of these singular Crustacea does not date from very 
long ago. The first form recorded is probably that described by Lepechin in the 
year 1780, as Oniscus scorpioides, which has turned out to he a species of the 
genus Diastijlis. Another Cumacean form was observed in the year 1804 by 
Colonel Montagu, and designated by the very same specific name ; but this 
author erroneously believed that the solitary specimen found was a defective 
l — Crustacea. 
