92 
FOSSIL FORAMINIFERA . 
“ (II.) N. variolaria from Stubbington, and 
“ (III.) N. variolaria from White-Cliff Bay, are exactly the same as the 
Belgian form. They belong to the type of the species. 
u It is remarkable that among your specimens there is not a single N. Heberti , 
which species is nearly always the companion of N. variolaria. In Belgium 
and France, in the upper part of the variolaria- beds there is usually one per cent, 
of N. Hebei'ti. In the lower beds (base of the “Laekenian”) these are more 
numerous (up to 50 per cent.). Is it that the Heberti is totally absent, or that 
the number of the specimens you kindly sent me are still too few for strict com- 
parison P This is an interesting question to solve. 
“ (IV.) My best thanks for the N. Prestwichiana , It. Jones. It arrives just 
at the moment to help me in the study of the Belgian N. planulata, var. a, vel 
minor , d’Archiac. This rare Nummulite, which I possess from Brussels, Jette, 
Wemmel, Laeken, Gand, and Briendareck in Belgium, is most polymorphic, 
but always different from N. planulata , Lam., and elegans , Sow. It shows the 
following varieties: — 
“1. Type : size 2-3 millim. ; shape irregular, lenticular, mucro in the centre, 
surface smooth. Wemmel and Jette. 
11 2. Var. plicata : size l-J-2 millim. ; shape lenticular, depression in the centre, 
surface plicated. Gand. 
“3. Var. granulata : size 1^-2 millim. ; shape flat, surface granulated. Brus- 
sels, Park St. Gilles. 
11 4. Var. minor : size 1 millim. ; lenticular, smooth, regular. 
“5. Var. Prestwichiana : size 1-2 millim.; flat, smooth, regular. 
u The spire is very nearly the same in all the varieties ; the last is always 
much larger than the foregoing whorl. By its variations this species has 
affinities sometimes with the N. variolaria, sometimes with Assilina , sometimes 
with Operculina. The difficulty now is what name to give to it. 
“You are the only one that has described and named it. The English speci- 
mens, however, are the most distant from the Belgian type. 
“ To take the English ones for a type is impossible ; they are so different from 
the majority that some palaeontologists would even consider them as a separate 
species. To transfer the name of N. Prestivichii to different forms as varieties 
of the same species, I cannot do without your permission. In fact I see only 
two ways of solving the question : either we can call the whole species 
N. Prestwichii, B.. Jones, and the English specimens var. planissima ; or we can 
call it N. Wemmellensis , as M. Vanden Broeck has suggested ; and then we have 
the name “ Prestwichiana ” to designate the variety you describe (Quart. Journ. 
Geol. Soc. vol. xviii. p. 93). You will kindly decide the question. 
“ I am now working out the Belgian Nummulites. I find in that country eight 
species, very distinct, and easy to separate. 
) 1. N. planulata , Lam., without central chamber, =j N. planulata, var., 
d’Arch., the large species. 
2. N. elegans , Sow., with central chamber, = N. planulata junior , d’Arch. 
) 3. N. Icevigata , Lam. (type, and vars. scabra , rotula, globidarid), without 
central chamber. 
4. N. Lamarcki, d’Arch., with central chamber. 
Ill I d’Arch., without central chamber, 
j 6. N. variolaria , Sow., with central chamber. 
{ 7. N. Orbignyi ( Operculina , Galeotti), without central chamber. 
8. N. Wemmellensis (or Prestwichii ) = N. planulata , var. a , vel minor , 
with central chamber. 
“ They make four pairs, of two species each, one species being without, the 
