JO 



vis blot Afslutningen af det sidste Segments ombøiede 

 Band. 



Bigenerina Sarsi n. sp. 



Fig. &— 0. 



Af Sand; mere eller mindre sammentrykt, tunge- 

 formet eller næsten aflangt triangulær. Spiralen 4 — 6-kamret, 

 Aabningen som hos Textularia; skiddengraa. 



Som bekjendt er der inden Slægten Biloculina paa- 

 vist Tilstedeværelsen af en A-form og en B-form, eler til- 

 sammen danner ea Art. Der findes ogsaa inden Bigenerina 

 Sarsi 2 konstante Former, der har saa mange Egenskaber 

 fælles, at de knapt kan karakteriseres som 2 særegne 

 Arter, desuden frembyder de i sin indre Bygning megen 

 Lighed med den Dannelsesmaade, der ligger til Grund for 

 de saakaldte A- og B-former hos Biloculina. 



A-formen begynder med et forholdsvis stort Embryo- 

 nalkammer, der har en Vidde af 0.06 mm. De fire føl- 

 gende Kamre tiltager raskt i Størrelse og afslutter Spira- 

 len, hvorpå a den biseriske Bygningsmaacle begynder med 

 smale og aflange Kamre, der efterhaanden vox er betyde- 

 ligt i Vidde, men derimod forholdsvis ubetydeligt i Længde. 

 0.52 mm. Station 192. 



B -formen har et meget mindre Embryonalkammer 

 euel A-formen. Det har nemlig blot en Vidde af 0.024. 

 Spiralen dannes af 5 — 6 Kamre, der er forholdsvis lige- 

 saa ubetydelige som det første Kammer. De følgende 

 Kamre tiltager langsomt saavel i Vidde som i Længde. 

 De er meget talrigere end hos A-formen, hvorfor ogsaa 

 B-formen opnaar en langt betydeligere Størrelse end A- 

 formen. 0.92 mm. Station 255. 



Lagena lucida Will. 



Af denne Art fandtes et typisk Exemplar i Bund- 

 prøven fra Station 192. Tidligere har jeg i noget Mate- 

 riale fra den norske Kyst, som Cand. Nordgaarcl sendte 

 mig, fundet et par Exemplarer af en Varietet, hvilken jeg 

 i Bergens Museums Aarbog for iaar 1 har beskrevet under 

 Betegnelsen Lagena Nordgaardi nov. var. Disse Exem- 

 plarer er næsten kugleformede, medens Exemplaret fra 

 Nordhavsexpeditionen er aflangt og fladtrykt paa Siderne. 

 'Alle disse Exemplarer viser den karakteristiske Hestesko- 

 formede Eortykkelse paa begge Sider af Kjølen. Denne 

 Fortykkelse er meget lidet ophøiet og deri samt i Muncl- 

 aabningens Form og Beliggenhed adskiller disse Exem- 

 plører sig fra Lagena. fasciata Egg. (Reuss, 1862, Die 

 Foraminiferen-Familie der Lagenideen, Sitz. Ber. Akad. 

 Wiss. Wien. Bd. XL VI, 1 Abt. p. 323, Pl. 2, fig. 24). 



Thalamophorernes geografiske Udbredelse. 



Søger man at fa a. et Overblik over Thalamophorernes 

 Forekomst over alle de af Norhavsexpeditionen undersøgte 



Report on Norwegian marine investigations 



drawing to be a second keel is probably only the termina- 

 tion of the backward-curved margin of the last segment. 



Bigenerina Sarsi n. sp. 



Figs. 5 — 6. 



Of Sand; more or less compressed, Ungulate or 

 almost an acute-angled triangle, the spirial 4 — G-chambered, 

 opening as in Textularia; of a dirty gray colour. 



The presence of an A-form and a B-form, as is 

 well known, has been demonstrated in Biloculina, the two 

 forms making one species. In Bigenerina Sarsi there are 

 2 constant forms, which have so many characters in com- 

 mon, that they can scarcely be defined as 2 different spe- 

 cies. Moreover, in their internal structure, they exhibit 

 a great resemblance to the mode of development which is 

 the foundation of the so-called A and B forms in Bilo- 

 culina. 



The A-form begins with a comparatively large em- 

 bryonal chamber, with a width of 0.06 mm. The 4 suc- 

 ceeding chambers increase rapidly in size and terminate 

 the spiral, whereupon the bi-serial mode of structure be- 

 gins with narrow, oblong chambers, which gradually ' 

 grow to a considerable widt, but, on the other hand, are 

 of no great length. 0.52 mm. Station 192. 



The B-form has a much smaller embryonal chamber 

 than the A-form, having a width of only 0.024 mm. The 

 spiral is formed of 5 or 6 chambers, which are relatively 

 as small as the first. The next suceeding chambers in- 

 crease slowly both in width and length. They are much 

 more numerous than in the A-form, so that the B-form 

 attains to a far larger size than the A-form — 0.92 mm. 

 Station 255. 



Lagena lucida Will. 



A typical specimen of this species was found in the 

 bottomsample from Station 192. I had previously found, 

 among some specimens from the Norwegian coast, sent 

 me by Mr. Nordgaard, a few specimens of a variety 

 which I have described in the Bergen Museum Year-book 

 for 1899 * under the name Lagein Nordgaardi, nov. var. 

 These specimens are almost spherical, while the specimen 

 from the North Atlantic Expedition is oblong and com- 

 pressed at the sides. All these specimens show the cha- 

 racteristic horse-shoe-shaped thickening on both sides of 

 the keel. This thickening is of no great elevation. To- 

 gether with the shape and position of the opening, it 

 separates these specimens from Lagena fasciata Egg. (Reus, 

 18(52, Die Foraininiferen-Familie der Lagenideen. Sitz. 

 Ber. Akad. Wiss, Wien. Vol. XLVI, 1 Abt. p. 323, PI. 

 2, fig. 24. 



The Geographic Distribution of the Thalamophora. 



In taking a survey of the occurrence of Thalamophora 

 in all the ocean-depths investigated by the Norh Atlantic 



1 Report on Norwegian marine investigations. 



