I. Pyrgo laeyis adskiller sig fra den ovennævnte 

 recente Art ved en noget mere hvælvet Form. 



II. Pyrgo laevis er blot fondet i de tertiære Afiei- 

 ringer ved Paris, hvilke rimeligvis er dannede paa forholds- 

 vis grandt Vand. 



Hertil skal jeg bemærke følgende: Schlnmberger har 

 som bekjendt paavist, at der inden de enkelte Arter af 

 Biloculiner findes en A-form og en B-form, der væsentlig 

 adskiller sig fra hinanden ved de indre Kammeres Anordning. 

 Af de mere end 100 Expl. af Biloculiner fra det norske Nord- 

 hav, gjennem hvilke jeg har gjort Snit lor at kunne se deres 

 indre Bygning, har jeg væsentlig fondet A-formen og sjeld- 

 nere B formen. Denne sidste adskiller sig fra A-formen 

 ialmindelighed ogsaa ved enkelte ydre Kjendetegn, nemlig 

 ved en noget betydeligere Størelse, mere hvælvede seg- 

 menter og mindre stærkt fremtrædende Kjøl, egenskaber, 

 som denne B-form har tilfelles med Pyrgo laevis. Dog 

 skal det bemærkes, at Pyrgo laevis ogsaa synes at have 

 mere hvælvede Segmenter end B-formen. Paa den anden 

 Side er der en anden fossil Art Biloculina amphiconica 

 Reuss, fondet i de tertiære Afleiiinger ved Wien, der saa 

 afgjort ligner A-formen fra det norske Nordhav, at der 

 her ikke længer kan være Tale om, at skjelne mellem 

 fossile og recente Arter. Rimeligvis har saaledes De- 

 france fondet B-formen og Reuss A-formen af en og 

 samme Art, dor altsaa endnu lever paa de store Dyb i de 

 arktiske Have. 



Schlumbergers B. Sarsi og Goes's B. laevis kan paa 

 ingensomhelst Maacle skilnes fra hinanden, hvad disse For- 

 fatteres Afbildninger og Beskrivelser godtgjør. Af de tid- 

 ligere fremførte Grunde mener jeg, at man er berettiget 

 til at benævne den i Norhavet funclne Form Biloculina 

 laevis. 



De af Brady i det nordlige Atlanteøhav fondue Ex- 

 emplarer af B. laevis synes at være meget abnormt dan- 

 nei'e. hvis de overhovedet kan henføres til denne Art. 

 Blandt alle de Biloculiner fra det norske Nordhav, 

 som jeg har havt til Undersøgelse, har jeg ikke fondet et 

 eneste Exemplar, der endog tilnærmelsesvis ligner de af 

 Brady afbildede Exemplarer af B. laevis De er ogsaa 

 alle dannede efter en ganske anden Formtypus end Bra- 

 dys Exemplarer. Hos disse sidste kan man ifølge Brady 

 tydelig skjelne mellem 2 ligeløbende Kjøle, idet de 2 sid- 

 ste Segmenters Bremmer er frie. Hos Nordhavsexpedi- 

 tionens ligesom ogsaa hos Goes's Exemplarer er nitid 1 det 

 sidste Segments Band voxet udover den yderste Rand af 

 det næstsidste Segment, saaledes at denne er fuldstændig 

 skjult. Kort sagt, Bradys Exemplarer er 2-kjolede, medens 

 de i Nordhavet fundne er l-kjølede Pyrgo laevis synes 

 ogsaa at være 1-kjølet, hvad Blainvilles Tegning ikke alde- 

 les tydelig viser, ialfald synes det næst sidste Segments 

 Rand at være dækket af det sidste Segment. Hvad der 

 paa Tegningen synes at danne en Kjøl No. 2, er rimelig- 



Paa fig. 915 hos Goes kan det ikke bestemt afgjøres om der 

 her ikke foreligger et 2-kjølet Exemplar. En Slibning er her 

 nødvendig. 



T. Pyrgo laevis differs from the above mentioned 

 recent species in having a more vaulted shape. 



II. Pyrgo laevis is only found in the tertiary 

 ' deposits near Paris, which have probably been formed m 

 comparatively shallow water. 



To this I will add that Schlumberger, as is well 

 known, has shown that in the different species of Bilocu- 

 lina, there is an A-form and B-form, which differ from one 

 another principally in the arrangement of the inner cham- 

 bers. Out of the 100 or more Biloculina specimens from 

 the Norwegian North Atlantic of which I have made sections to 

 enable me to see their internal structure. I have princi- 

 pally found the A-form, and less frequently the B-form. 

 The latter also generally differs from the A-form in cer- 

 tain external distinguishing features, more especially in 

 tis somewhat larger size, its more vaulted segments, and 

 its less strongly marked keel, features which this B-form 

 has in common with Pyrgo laevis. I must, however, be 

 observed that Pyrgo laevis also seems so have more vaul- 

 ted segments than the B-form. On the other hand, another 

 fossil specis, Biloculina Amphiconica Reuss, was found in 

 the Tertiary deposits at Vienna, bearing such a strong 

 resemblance to the A-form from the Norwegian North 

 Atlantic, that there can be no longer any question here of 

 destinguishing between fossil and recent species. It is 

 thus probable that Defrance has found the B-form and 

 Reuss the A-form of the same species, which thus still 

 lives at great depths in the Arctic Ocean. 



Schlumberger's B. Sarsi and Goes's B. laevis can in 

 no way be distinguished from one another, a fact which 

 is proved by the illustrations and descriptions of the 

 above-named writers. For reasons already given, I consi- 

 der it justifiable to designate the form found in the Nortli 

 Sea, Biloculina laevis. 



The specimens of B. laevis found by Brady in the 

 North Atlantic, seem to be of a very abnormal formation, 

 if indeed they can be placed in this species at all. Among 

 all the Biloculina from the Norwegian North Atlan- 

 tic, which I have had for investigation, I have not 

 found a single specimen winch resembles even approxima- 

 tely the specimens of B. laevis figured by Brady. They 

 are also all formed after an altogether different type form 

 to that of Brady's specimens. In the latter according to 

 Brady, it is easy to distinguish between the two parallel 

 keels, the rims of the last two segments being free. In 

 the North Atlantic Expedition, and also in Goes's, the 

 margin of the last segment has always l grown out over 

 the extreme margin of the penultimate segment, so as to 

 hide it completely. In short, Brady's specimens have 2 

 keels, while those found the North Atlantic have 1 keel. 

 Pyrgo laevis also seems to have 1 keel, a circumstance 

 which is not shown at all clearly in Blainville's drawing. 

 At any rate, the margin of the penultimate segment seems 

 to be covered by the last segment. What appears in the 



In Goes's fig. 915 it cannot be certainly determined whether 

 the specimen represented may not be double-keeled. A 

 section is required here. 



