﻿Crustacea Malacostraca. II, 



By 



H. J. Hansen. 



IV. The Order Tanaidncea. 

 I ntroduction. 



Before entering on tlie subject of the ])resent pa^jcr I nia\ refer to tlie "Introductory Remarks" in 

 "Crustacea Malacostraca I" [lublishcd in igo8, Ijecause tlie>- contain various statements tliat need not 

 to be repeated here. In that chapter I explained the limits of the area investigated bv the "Ingolf and 

 other Danish expeditions to our northern dependencies; the principal sources (apart from the "IngolTi for the 

 material examined were enumerated and tlie principles followed as to "occurrence" and "distribution" 

 were laid down. Zoologists wishing to get .some information on these and allied topics nia\- find them 

 in the paper mentioned. 



Our earlier knowledge of the Tanaidacea inhabiting the seas around Greenland, Iceland and 

 the Fieroes was poor. Only 9 species were known, 2 of which belong to the famil\- Apseudidjc, 7 to 

 the Tanaidte. I am, however, inclined to think that no Carcinologist would have supposed that it 

 might be possible to discover more than ten or fifteen new species within that area. Hut in the 

 present paper I enumerate 78 specie.s, all, excepting one, captured b\ Danish expeditions, and 52 of 

 these species are new to science. The "Ingolf" has secured 71 of the species, but of these 13 have 

 besides been taken by another Danish expedition or b\- two or more zoologists; 3 species have been 

 gathered only by the "Thor" (Dr. Joh. Schmidt), 2 species exclusively by the second Amdru])-lvxpedition 

 (Mag. so. Soren Jenseni and a single species by other zoologists. In proportion to the number of 

 species of Tanaidacea hitherto known from Norway, from Oreat Rritain or from all seas together the 

 "Ingolf" collection is so astonishing, that some special reason ma\' be loi)ked for; it may be of 

 interest to attempt a discussion of the topic, and it may be possible to point out some results of 

 more general significance. h"iiiall\ a treatment of some other results and cjuestions ma\ be inserted 

 before the purel\' systematic part. 



On the Literature. 



The earlier literature until the vear 18S1 comprises a good nnnil)er of papers, but most among 

 them dealing with onl\- a single form or with some few s]iecies; the largest and most wnlnable of 

 these contrilnitions were written by H. Kroyer (1842I and W. Lilljeborg 118C15I. But in 1881 Ot. ( ). Sars 

 pul)lished his ]iaper: Kexision af C.ruppen: Isopiuid clh-lifrra (Arch. Math, og Natur\-. l!d. 71, which is 

 epoch-making in the historx' of our order. He dixided it In- named it a group into two well- 



Tin.- inyoii-ixpcjiiion. Ill, ;. ' 



