﻿CRUSTACEA M A LACOSTRACA. 



ill a completely satisfacton' manner, but on the other hand one can set up a lon^^ series of excellent 

 groups with one to several families in each group. Meanwhile, for the sake of a general view, the 

 old division into Brachyura, Anomura and Macrura is retained. 



The "Ingolf's catch of Decapoda was relatively not large; the northerly seas, as is well-known, 

 are tolerably poor in species of this order. Nevertheles.s, the following account will give an important 

 addition to the geographical distribution towards the north of a number of the deep-water forms 

 known from somewhat more southerly regions of the Atlantic. Especially interesting in this regard is 

 a comparison with the fauna kuown, as the result of the American deep-water investigations and 

 S. I. Smith's excellent descriptions, from the tract between ca. 35 and 45'' N. L. off the east coast of 

 America. It appears that most of the deep-water species collected by the "Ingolf outside of the cold 

 area are noted by Smith from the region mentioned, but this author has certainly three to four times 

 as many species as the "Ingolf. The Danish ship has not made nearly so many hauls in deep water 

 on bottom with j^ositive temperatures as the Americans: if we had had several times more dredgings 

 from the waters south of southerly (yreenland, we should quite certainl\- have obtained manv more of 

 the species known from about 40" N. L., but I doubt whether we should have got much more than 

 the half of Smith's species. Although the investigations are thus far from sufficient to show the true 

 extent of the decapod deep-water fauna of the most northerly parts of the Atlantic in comparison with 

 that of more southerly latitudes, yet the following account will give very interc'^ting and new information 

 regarding the distribution of a number of more southerly species far to the north in deep-water areas, 

 the coastal fauna of which has a somewhat arctic character. On the other liand, it can be said that 

 of the Decapoda living from the beach down to ca. 200 fm. in the waters round (ireenland and Iceland 

 as also on the north and west sides of the F'leroes extremely few .species will be discovered in future 

 which are not dealt with in this work. More exact knowledge however mav naturally be gradually 

 obtained of the geographical and bathymetric distribution of the \-arious species within the region 

 mentioned, and especially a much more complete knowledge than the present concerning the tempera- 

 ture occurring at the coldest and in the warmest periods of the \ear in the depths in which the 

 species live at their different localities. 



After these remarks this may perhaps be a suitable place to insert some critical n<)tes on an 

 apparently somewhat variable yet very wide-spread view regarding what is meant by arctic and 

 boreal or subarctic, that is, on the zoogeographical question concerning the fauna, both coastal 

 and deep-water fauna, in the more northerly seas of the globe. It is in other words the marine 

 Arthropoda in the great, as yet incomplete, work Faun a Arctica published by F. Romer and F.Schau- 

 din n — which requires a closer investigation. Most of the contributions published hitherto (1906) are almost 

 entirely compilations, as the material the various contributors ha\e had from the "Helgoland" Ex- 

 pedition is comparatively speaking extremely small. One of the carcint)logical papers in this work is 

 almost quite u.sele.ss, and of others it may be said that their plan and execution are .so mifortunate 

 that they will certainly contribute more to confuse than to clear up the ideas on arctic and boreal 

 fauna in the minds of the majority of the Zoologists who may use them. I was led into this literary 

 investigation by becoming acquainted with Dr. F. Dof lein's treatment of the Deca]ioda in "I'auna .Vrc- 



