[SCIENTIFIC RESULTS OF THE PHILIPPINE CRUISE OF THE FISHERIES STEAMER 

 "ALBATROSS," 1907-1910.— No. 33.] 



THE EUPHAUSIACEAN CRUSTACEANS OF THE "ALBA- 

 TROSS" EXPEDITION TO THE PHILIPPINES. 



By H. J. Hansen, 



0/ Copenhagen, Denmark. 



INTRODUCTION. 



At the request of the Commissioner of Fisheries, I promised to 

 work up the Schizopod Crustaceans and Sergestidae gathered by the 

 United States Fisheries steamer Albatross during the Phihppine 

 expedition of 1907-1910, and the present paper, which is the first 

 instalment, deals with the order Euphausiacea. Before entering on 

 the description of the genera and species it may be appropriate to 

 give a brief introduction. 



The Schizopoda and the Sergestidae are aU free-swimming through- 

 out life and may occur near the bottom, but are most often truly 

 pelagic, living near the surface or in deeper layers of the ocean. 

 Many species, especially of the order Mysidacea, inhabit shallow 

 water not. far from the coast; while most of the Euphausiacea and 

 many Sergestidse are truly oceanic. Consequently only a small num- 

 ber of the specimens, and especially of larger forms, were taken in the 

 trawl or the dredge, the large majority having been secured in nets 

 with other Plankton. Only a small portion of the animals had been 

 sorted, but I received a large number of bottles containing Plankton 

 samples. From the great majority of these samples aU Schizopoda 

 and Sergestidge were removed under my supervision, but as several 

 of the large bottles contained an immense number of these Crustacea, 

 about one-third of the contents was taken out and the Schizopoda, 

 etc., separated. 



As the material of the Crustacea mentioned is very large, I found 

 it necessary to divide it into three portions according to orders. 

 Although the material of the Euphausiacea is larger than that of the 

 two other groups, it was selected because I was sure that nearly aU 

 species were known beforehand, as most of the forms of this order 

 have a very wide geographical distribution, and I had worked out the 

 Schizopoda from the Dutch Siboga expedition, which had explored an 

 adjacent area, namely, the seas and straits in the Indian Archipelago. 



Proceedings U. S. National Museum, Vol. 49— No. 2129. 



635 



