302 On the Nomenclature of the Foraminifera. 



others have been larger individuals picked out by means of 

 hand-lenses from the coarser dust of the disintegrated material. 

 The great difference of size, however, among individual Fora- 

 minifera carries but little weight in the determination of spe- 

 cies ; for the conditions, not only of growth, but of feeding- 

 ground, depth of water, and climate affect them so greatly, 

 that a form which may be gigantic in one habitat will be 

 arrested or dwarfed in another, retaining all the essential cha- 

 racteristics of shape and structure which are required for its 

 specific identification. 



With respect to the Foraminifera Rotalina (Carpenter) of 

 the English and European Chalk, we may notice that among 

 Ehrenberg's figures we recognize : — 



Planorbulina farcta [F. & M.). 



Haidingerii (i)'0r5.). 



ammonoides (Rss.). 



ariminensis [I)''Orh.). 



globulosa [Ehr.) . 



Pulvinulina spatiosa (Ehr.). 



truncatulinoides (D^Orb.). 



Micheliniana [D'Orb.). 



caracolla (Rcem.). 



D'Orbigny found in English Chalk all the Rotalines he got 

 from the French Chalk (see above, p. 295). In our own col- 

 lection we have from — 



1. The Upper Chalk of Thorjje, near Norwich : — 



Planorbulina ammonoides [Rss.). 



Ungeriana [D'' Orb.). 



Haidingerii (D'Orb.). 



(Truncatulina) lobatula {W. <£; J.). 



Rotalia umbilicata, i)' Orb. 



2. The Chalk of Gravesend: — 



Planorbulina ammonoides {Rss.), 

 Ungeriana (D^Orh.). 



(Planulina) ariminensis (D^Orb.). 



(Truncatulina) lobatula {W. & J.). 



Pulvinulina Micheliniana {D Orb.). 

 Rotalia umbilicata, i)' Orb. 



Of most of these there are also local subvarieties, corre- 

 sponding more or less closely not only with those named by 

 D'Orbigny, but also with many of iho, numerous Rotaline 



