50 



Ler. som ikke er noget almiudeligt Forekomststed for hine 

 Foraminiferer, eller som altsaa ligger imellem Kystleret og 

 det saakaldte Biloculinler, bar jeg paa Kartet afgrændset 

 for sig selv under Navn af Overgangsler. 



Det forholder sig imidlertid ikke sadledes, at det graa 

 Ler ophører, hvor det brune begynder at forekomme. Tvert- 

 imod tinder vi ofte. at det forstnævnte vedbliver at udgjøre 

 det underste Lag af Bundprøveh selv indenfor det egentlige 

 Biloculinlers Omraade. Det viser sig saaledes. at det brune 

 ■Sediment kun meget langsomt tiltager i Mægtighed. Paa 

 tiere af Expeditionens Tversnit fandtes det graa Ler som 

 en væsentlig Del af Bundprøven indtil en Afstand af ca. 

 15 Mile fra den første Station. hvor det brune Ler havde 

 begyndt at vise sig. Et Par af de Bundprover. der var 

 optagne paa meget store Dyb (over 1700 Favne), bestod 

 udelukkende af graat Ler og indeholdt kun ganske smaa 

 Mængder af det brune. Disse Observationer tyder paa. at 

 Biloculinleret er en Dannelse af ringe Mægtighed. hvilende 

 paa et underliggende Lag af graat Ler. Dette stadfæstes 

 end yderligere ved Skrabningerne. under hvilke en Mængde 

 graat Ler optoges paa de største Dybder. 



I Overgangsleret forekommer Biloculiner og de øvrige 

 Dybvands-Foraminiferer blot spredt og enkeltvis. Skjønt 

 det derfor i Almindelighed kun bruser svagt for Syrer, 

 hænder det dog stundom, at Kalkgehalten er temmelig be- 

 tydelig, selv om ingen Skaller kan iagttages hverken i det 

 oprindelige Ler eller i dets Residuum efter Slemning. 



Indenfor de Grændser. hvor de ovennævnte Foramini- 

 ferer optræder med Regelmæssighed og i større Antal, ei- 

 det brune Ler meget fint og ensartet og synes selv under 

 en stærk Lupe kun at beståa af amorfe Partikler. 



Biloculinlerets brune Farve kan være mere eller min- 

 dre udpræget. Nogle Bundprøver er lyse gulbrune, andre 

 morkbrune. i fugtig Tilstand næsten chokoladefarvede. Tal- 

 rige smaa. hvide Foraminiferer bidrager naturligvis til at 

 give Leret en lysere Farve. 



Ved Slemning af Biloculinleret erholder man et større 

 eller mindre Residuum, der væsentlig bestaar af Foramini- 

 ferer af forskjellig Størrelse, Form og Farve. Under Lupen 

 viser det sig dog, at nogle yderst smaa, runde Kalkskaller 

 med et tydeligt Kammersystem er langt overveiende i Antal 

 fremfor de øvrige. Professor Gr. 0. Sårs bar været af den 

 Godhed at bestemme disse Dyr for mig. Han bar fundet, 

 at de hører til de meget bekjendte "Grlobigeriner", men at 

 de er meget mindre udviklede med Hensyn til Størrelse 

 end de, der forekommer i de sydligere Have. 



Da disse Dyr overalt i Nordhavet er Biloculinernes 

 uadskillelige Ledsagere, kunde maaske det ber omhandlede 

 Sediment ogsaa gaa ind under Navnet -'Globigerinler". en 

 Betegnelse, der er blevet benyttet i de britiske Expeditioners 

 Rapporter. Ifølge John Murray skal dette Sediment, hvis 

 nifst typiske Eiendommelighed er dets Rjgdom paa Grlobi- 

 geriner, forekomme i stor TJdstrækning i det af Challenger- 

 expeditionen beseilede Hav. hvor det er fundet paa de Heste 



of the brown clay. The strip of brown clay, varying in 

 width. where that deposit does not regularly contain Bilo- 

 culinæ, I have marked off on the map as a separate forma- 

 tion, under the name of transition clay. 



Meanwhile. it is by no means to be supposed that 

 the grey clay suddenly terminates where the brown begins 

 .to occur. On the contrary, the former deposit was fre- 

 quently found to constitute the under layer of samples brought 

 up trom within the limits of the true biloculina formation. 

 Vertically, tberefore. the increase of the brown deposit is 

 very slow. In several of the localities of the tract explored. 

 the grey clay was found to constitute a large part of every 

 sample, within a distance of 15 geographical miles from 

 the first Station at which the brown clay occurred. One 

 or two samples, obtained from great depths (upwards of 

 1700 fa thorns), consisted almost exclusively of grey ' clay, 

 the admixture of brown deposit being very small. From 

 these data. Biloculina clay is shown to be a deposit of 

 trilling vertical extent, with an uriderlying laver of grey 

 clay. Moreover. a good deal of grey clay came up in the 

 dredge from the greatest depths. 



In the transition clay, Biloculinæ and the other deep- 

 sea species of Foraminifera occur but occasionallv, and 

 scattered. Hence, though as a rule, tberefore. that deposit 

 effervesces very slightly with acids. the proportion of lime 

 is sometimes considerable, even when no calcareous shells 

 can be detected either in the clay itself or the residue left 

 on washing it. 



When regularly characterised by the presence of the 

 above-mentioned Foraminifera in considerable numbers, the 

 brown clay is an exceedingly fine and homogeneous deposit, 

 and would appear, even if examined under a powerful 

 magnifier, to consist of amorphous matter. 



The brown colour of Biloculina clay varies consider- 

 ably in depth and distinctness. Some of the samples were 

 light yellowish-brown, others dark-brown, — nay almost of 

 a chocolate sha.de in a damp state. Numbers of minute 

 white Foraminifera naturally contribute to give the clay a 

 whiter tint. 



On washing Biloculina clay. there is a greater or less 

 residue. which ohiefly consists of divers species of Fora- 

 minifera, varying in magnitude, form. and colour. With 

 the aid of a lens, minute, round, calcareous shells having 

 a distinct system of chambers are found to exceed by far 

 in number the other animal remains. Professor G. O. Sårs 

 has bad the kindness to determine these animals. He 

 found tbem to be known Gldbig&rince, though much less 

 developed in point of size than the species which occur in 

 the Southern Seas. 



These animals invariably accompanving Biloculinæ in 

 the North Atlantic, the brown deposit heiv treated of might 

 be also termed "Grlobigerina clay," a designation adopted 

 in the Reports from the various British Expeditions. Ac- 

 cording to Mr. John Murray, this sedimentarv substance, 

 whose chief tvpical characteristic consists in the presence 

 of great numbers of Qlobigerinæ, occurs extensively through- 

 out the tracts of ocean investigated on the "( 'ballenger" 



