MORPHOLOGY OF THE SCHIZOPODA. 



All the priueipal types of this group being represented in the collection made during 

 the Challenger Expedition, it may, I think, be apposite to discuss here in what relation the 

 Schizopoda stand to other Crustacea, and what is the systematic position to be at present 

 assigned to these forms, as also how the group may properly be subdivided. 



As is well known, Milne-Edwards, the great reformer of carcinology, ranked these 

 Crustacea, of which, however, a few forms only had at that time been recorded, side by 

 side with the Squillacea in his order Stomatopoda, ranging also therein the genus Leucifer 

 together with certain spurious genera, that since then have been found to be only larval 

 forms of other known Crustacea. Dana, in his great work on the Crustacea of the 

 United States Exploring Expedition, adopts the views of Milne-Edwards as to the 

 systematic position of the Schizopoda, ranging them in his order Anomobranchiata, which 

 perfectly corresponds with the order Stomatopoda of the first named author; and several 

 other carcinologists have since then done the same. Such a classification must, however, 

 in my judgment, at present be regarded as decidedly unsatisfactory, the Schizopoda 

 being undoubtedly much more nearly related to the Eubranchiata or Decapoda of Milne- 

 Edwards than to the Anomobranchiata (Stomatopoda). It will, I think, be absolutely 

 necessary to restrict the order Stomatopoda to the Squillacea only, a group of Crustacea 

 differing in many points very materially from all other Podophthalmia, whereas the genus 

 Leucifer may find its appropriate place side by side with Sergestes, among the lower Deca- 

 pods (Penseidea). Thus the Schizoj)oda are either to be regarded as forming a distinct order, 

 or to be ranged in the order of the Decapoda or Eubranchiata of Dana. The last men- 

 tioned view lias also been held of late by several distinguished modern zoologists, and 

 the striking similarity in their external form often exhibited by these Crustacea to the 

 lower Macrura (Caridea), has even led certain of these zoologists to regard the Schizopoda 

 as merely forming a section of that tribe of the Decapoda. In my opinion, however, 

 it is more appropriate at present to assign to this group the rank of a distinct tribe 

 or suborder, there being several well-marked characters distinguishing these Crustacea 

 rather sharply from all other known Decapods. 



Of such characteristics peculiar to the group, the following may be set forth : — 



1. The presence of strongly developed natatory branches (exopods) on all the limbs 

 of the trunk or legs is, perhaps, the most striking feature distinguishing this group, and 



