12 



kunne have Grand til at kalde denne Strækning Uvigeri- 

 naler, især da denne Art her opnaar en betydelig Stør- 

 relse, medens den paa de nordlige og østlige Dele oftest 

 er forholdsvis sjelden og degeneret. 



Det graa Ler ved Jan Mayen og Island synes i det 

 store og hele at have samme Karakter som Leret ved 

 Norges Kyst. At en Art mangler snart her snart der 

 beror vel oftest paa en Tilfældighed og berettiger saaledes 

 ikke til at drage faste Slutninger med Hensyn til Arter- 

 nes Udbredelse. Mange Thalamophorer er jo meget spar- 

 somt repræsenteret paa de enkelte lokaliteter og kan vel 

 ogsaa ved et Tilfælde oversees ialfald de ubetydelige og 

 mindre iøinefaldende Arter. 



Som tidligere bemærket, har jeg delt det graa Ler i 

 2 forskjellige Udbredelsescentrer. Det nordlige af disse 

 Centrer udmærker sig nemlig ved Forekomsten af nogle 

 arktiske Former, der enten mangler eller ialfald optræder 

 langt sparsommere paa det Omraade, der hører til det 

 sydlige Centrum. Som saadanne kan nævnes: Astrorhiza 

 crassatina, La gena apiculata, Pulvinulina Karstenii, og 

 Globigerina pachyderma. Paa den anden Side er der 

 endel sydlige Arter, der inden det nordlige Centrums om- 

 raade enten aldeles mangler eller ialfald forekommer me- 

 get sparsomt og uden at opnaa sin falde Størrelse, f. Ex. 

 Bulimina margin ata, Uvigerina pygmaea og angulosa, Oper- 

 culina ammonoides. Forøvrigt synes Talamophorfaunaen 

 over hele det graa Ler at være meget ensformig. 



Bhabdamminaleret, Hvad der især karakteriserer 

 denne Lersort er foruden dens graagrønne Kulør tillige 

 dens Overflod paa Exemplarer af Rhabdammina abysso- 

 rum. Af de hyppigst forekommende Thalamophorer kan 

 nævnes: Tholosina bulla, Cassidulina laevigata, Truncatu- 

 lina lobatula og refulgens, Pulvinulina Karstenii, Nonionina 

 umbilicatula, Quinqueloculina seminulum og tricarinata. 

 Forresten synes de enkelte Arter ialmindelighed at fore- 

 komme meget spredt og i ringe Antal paa hver Lokalitet. 

 Slægterne Lagena og Biloculiua, der ellers ialmindelighed 

 er godt representeret, udmærker sig her ved sin Fattigdom 

 paa Arter og Exemplarer. 



Globigerina bulloides, pachyderma samt talrige Over- 

 gangsformer mellem disse to Arter er almindelige over 

 hele det graa Ler. Paa den sydlige Del af Omraadet, 

 specielt langs den norske Kyst synes de fleste Exemplarer 

 at høre til Gl. bulloides og de nævnte Overgangsformer, 

 medens Gl. pachyderma især er almindelig paa Bhabdam- 

 minaleret og ved Spidsbergen. 



Overgangsleret er overorclentligt rigt paa Thalamo- 

 phorer. Specielt har jeg i en enkelt Bundprøve (fra Sta- 

 tion 192) fundet en usædvanlig Mængde Arter, nemlig 

 over Halvparten af samtlige i Nordhavsexpeclitionens Ma- 

 teriale forekommende Arter. Grunden til dette rige Dyre- 

 liv er vel den, at saavel de paa elet grundere Vand som 

 de paa Havets Dybder levende Dyreformer her blander 



is present in particularly large number in the southern 

 portion of the gray clay, so that one might be tempted to 

 call this region Uvigerina Clay, especially as that species 

 here attains a considerable size, while in the northern and 

 eastern parts it is often comparatively rare and degenerated. 



The gray clay near Jan Mayen Island and Iceland, 

 seems, on the whole, to have the same character as the 

 clay on the Norwegian coast. That a species is absent 

 now in one place, now in another, must generally be due 

 to chance, and therefore does not justify the drawing of 

 decided conclusion with regard to the distribution of the 

 species. Many Thalamophora, indeed, are very poorly 

 represented in certain localities, and may even happen to 

 be overlooked, at any rate smaller and less conspicuous 

 species. 



As previously mentioned, I have divided the gray 

 clay into 2 different centres of distribution. The more 

 northerly of these two centres is characterised by the occur- 

 rence of some arctic forms, which are either absent, or at 

 any rate appear far less frequently, in the region belon- 

 ging to the southern centre. Among these may be named 

 Astrorhiza crassatina, Lagena apiculata, Pulvinulina Kar- 

 stenii and Globigerina pachyderma. On the other hand 

 there are some southern species which are either altogether 

 absent from the field of the northern centre, or at any 

 rate are vere scarce, and do not attain to their full size. 

 e. g. Bulimina marginata, Uvigerina pygmæa and augulosa, 

 Operculina ammonoides. Moreover, the Thalamophora 

 fauna throughout the gray clay, seems to be very homo- 

 geneous. 



The Rhabdammina Clay. That which, in addition 

 to its gray green colour, especially characterises this kind 

 of clay, is its superabundance of specimens of Bhabdammina 

 abyssorum. Among the Thalamophora most freqently oc- 

 curring, we may mame Tholosina bulla, Cassidulina laevi- 

 gata, Truncatulina lobatula and refulgens, Pulvinulina Kar- 

 stenii, Nonionina umbilicatula, Quinqueloculina seminulum 

 and tricarinata. The different species appear generally 

 to be very scarce, and in small numbers at each locality. 

 The genera Lagena and Biloculina, which are elsewhere 

 well represented, are here characterised by their poverty 

 of species and specimens. 



Globigerina bulloides, pachyderma, and numerous 

 transition forms between these two species are general 

 throughout the gray clay. In the southern portion of the 

 region, especially along the Norwegian coast, most of the 

 specimens seem to belong to Gl. bulloides and the above- 

 mentioned transition forms, while Gl. pachyderma is espe- 

 cially common in the Bhabdammina Clay and off Spitz- 

 b ergen. 



The transition clay is exceedingly rich in Thala- 

 mophora. In one sample (from Station 192), I have found 

 an unusual number of species, that is to say, more than 

 half the species occurring in the North Atlantic Expedi- 

 tion collection. The reason for this luxuriant animal life 

 is probably that the animal forms, both in the shallower 

 w r ater, and in the occean depths, mingle here, and find the 



