INTRODUCTION. v 
The few kinds of Foraminifera yielded by the Chillesford Crag, a deposit regarded by 
Messrs. Wood and Prestwich (‘ Quart. Journ. Geol. Soc.,’ vol. v, p. 350) as probably 
contemporaneous with the Crag of Norwich (Mammaliferous Crag), by Mr. S. Wood, 
jun.,’ as subsequent to it, and by the Rev. O. Fisher’ as being older than the Norwich 
Crag, indicate a rather shallow and cold sea, perhaps somewhat brackish too, as their pro- 
bable habitat. They are Polymorphina lactea, Bulimina elegans, Truncatulina lobatula, 
Rotahia Beccaru, Polystomella crispa, and P. striato-punctata. Mr. Prestwich’s observa- 
tions (loc. cit., p. 351) on the probable influence of cold currents from the northern seas 
on the fossil fauna at Chillesford coincide with the above remarks. 
Lastly, some Foraminifera collected by Mr. H. C. Sorby, F.R.S., from the Brid- 
lington Crag® some years ago, and kindly placed at our disposal, have to be noticed. 
These comprise Cornuspira, Miliola, Lagena, Dentalina, Cristelluria, Polymorphina, 
Cassidulina, Truncatulina, Polystomella, and Nonionina, and are the most conspicuous 
of a probably more extensive fauna, nearly allied to that of the Suffolk Crag. 
With regard to our treatment of the generic and specific grouping of Foraminifera in 
this Monograph, having repeatedly stated our views as to the necessity of allowing a wide 
margin for variation from any central type in determining species amongst the Protozoa, 
we need not again enter largely upon the subject. Every extension of research tends 
more and more to show that such characters as surface-markings, form of aperture, 
number of chambers, and direction of growth—peculiarities upon which not only 
species and genera, but even families, have been constituted—are individually of 
little value in forming an estimate of the essential characters of a species among Fora- 
minifera. Neither need we ‘repeat what we have before said on the expediency of 
retaining (with this reservation as to the significance to be attached to them) the binomial 
appellations that have been given to well-marked varieties, regarded by others as specific 
forms. We shall have occasion to use them in the course of the Monograph ; and, as 
they will stand in the place of true specific names, we must refer our readers to the Table 
of 'l'ype-species, in the Appendix, for the alliances of these sub-species or varieties. By 
these remarks, we would not be thought to underrate the value of even trivial external 
features, such as those alluded to, for they are often of considerable significance both to 
the Zoologist and the Palzontologist; but only to caution those not practised in inves- 
1 See his paper mentioned at page ii. 
2 “Quart. Journ. Geol. Soc.,’ vol. xxii, p. 19, 1866. 
3 Mr. Bean wrote of the Bridlington Crag in 1835, ‘ Mag. Nat. Hist.,’ vol. viii, p. 355; and Sir C. Lyell 
in 1839, ‘Mag. Nat. Hist.,’ new series, vol. iii, p. 313. See also Phillips’s ‘ Geol. Yorkshire,” 1829, 
vol. i, p. 69; and H. C. Sorby’s paper on this Crag, in the ‘Proceed. Geol. and Polytech. Soc.,’ West 
Riding, Yorkshire, 1857-8, iii, p. 555. There is also a paper on the Bridlington Crag, by Dr. 8. P. 
Woodward, in the ‘ Geol. Mag.,’ 1864, vol. i, p. 49. 
