g CRUSTACEA MALACOSTRACA. 



tica" (B. I, p. 313—62), and it will not be denied that I have the most valid reasons possible foi 

 making a very detailed reference to this work, which deals with all the Decapoda taken north of 

 60 ° N. L. and likewise includes a number of forms only taken much farther south. Further, in an 

 extensive foot-note I shall make some remarks on one of the other papers so far published on the 

 Arthropoda in 'Fauna Arctica", namely, the work on the Pantopoda; this latter work is in one way 

 excellently suited to serve as a type and there are also special reasons for mentioning it more parti- 

 cularly, as the work on the "Ingolf's Pantopoda is referred to in it. 



As an introduction to my remarks on the part of "Fauna Arctica" which concerns me most, 

 the following may be mentioned. A destructive criticism of the principle underlying the choice of 

 the boundary between arctic and boreal fauna, which is followed by H. Ludwig in his treatment of 

 the Holothurida (and Asterida) in the work mentioned, has come from Dr. Hj. Ostergren (Bergens Mu- 

 seums Aarbog 1902, No. 9). Ostergren states, that Ludwig has simply taken the polar circle (i. e. 66 2 / 3 ° 

 N. L.) as this boundary-line, whereas it has long been known, that on the American coast Cape Cod 

 at 42 N. L. forms the boundary between the arctic and the boreal coastal fauna, and on the other 

 hand the west coast of Norway and its fjords right up to the North Cape, 71° 10' N. L., has an 

 essentially boreal fauna both as regards even the more littoral (0—50 fan.) and especially the areas in 

 deeper water (100—400 to 500 fan.). He does not enter into details regarding the more littoral fauna from 

 the North Cape to Nova Zembla. The geographical boundaries for the true deep-water fauna are 

 entirely different, as the cold area of the Northern Ocean with bottom-temperatures under o c C. 

 extends between the ridge off Norway on the one side and Iceland and the Faeroes on the other, 

 then in between the Faeroes and Scotland almost to 60 ° N. L. (the boundaries of the cold area can 

 be seen in the work on the Norwegian North-Atlantic Expedition), and with Ostergren one may 

 suitably choose 0° C. as the boundary for the arctic deep-water fauna. It may be recalled here that 

 we find positive bottom-temperatures to the west of the cold area, and the deep water of the Atlantic 

 with a part of its fauna pushes up into Denmark Straits and Davis Straits. 



Ludwig's work is chiefly a compilation, and Ostergren shows a number of errors of different 

 kinds and origin. But Ludwig in the opinion of Zoologists expert in his subject has published ex- 

 tremely valuable systematic papers on Holothurida etc., whilst several of the other contributors to 

 "Fauna Arctica" have certainly known comparatively little of the groups on which they wrote, a fact 

 which now and then is not without some influence on the compilation. 



We may turn now to the consideration of Doflein's work on the Decapoda. On p. 316 the 

 author writes: "Ich habe mich — — — zu einem Kompromiss entschlossen, indem ich diejenigen de- 

 kapoden Krebse auffuhre, welche die Meere nordlich von 6o° 11. Br. regelmassig beherbergeu; dabei 

 habe ich aber die Angehorigen arktischer Familieu, welche sich infolge von besonderen Verhaltnissen 

 weiter nach Suden ausbreiten, mitberiicksichtigt, so besonders die Bewohner der Kaltwassergebiete an 

 der Ost- und Westkiiste von Nordamerika. Haben doch die Erfahrungen der letzten Jahrzehnte be- 

 wiesen, dass Tiefseeformen siidlicher Gebiete nicht selten das Flachwasser der kalteu Zonen bewoh- 



nen; -". If the "sudliche Gebiete" mean the Gulf of Gascogne or the region explored by the 



"Travailleur" and "Talisman", it will be extremely difficult and probably impossible, to show a single 



