LOWER CHALK—MICROGRAPHIC STRUCTURE* 
309 
Family. 
Genera. 
No. of 
Species. 
— 
Textulariidee - 
Textularia 
9 
One new species. 
Verneuilina - 
2 
Tritaxia - 
2 
,■ ^ 
Spiroplecta 
2 
Gaudryina 
5 
One new species. 
Bulimina 
9 
Bolivina - 
1 
Pleurostomella 
2 
One new species. 
Lagenidu 
Lagena - 
2 
Nodosaria 
4 
Frondicularia - 
2 
Bhabdogonium 
1 
Marginulina - 
1 
■■ ; ; $ 
Vaginulina 
2 
Cristellaria 
7 
Polymorphina 
1 
;V ■ - V 
Ptamulina 
2 
Globigerinidie 
Globigerina - 
3 
Itotaliidse 
Discorbina 
1 
Truncatulina - 
1 
Anomalina 
1 
Pulvinulina 
1 
Bmtalia - 
2 
The total number of species is 82, and of these fifty-eight 
occur in the Gault, sixteen do not occur in that deposit, and 
eight are new to science. The assemblage as a whole is very 
similar to that of the underlying zone, though it contains three 
genera not recorded in the latter, viz., Placopsilina, Lituola and 
Pulvinulina; on the other baud, Ho example of the genus 
Flabellina has been observed in this zone. 
The difference in the Foraminifera found in the specimens from 
North-west Norfolk and north of the Wash, when compared with 
those from the same zone in the Midland and Southern Counties, 
is even more striking than in the zone of Am. vcirians. Thus 
in the acid residues (the northern chalk is too hard to wash) of 
five specimens from North-West Norfolk, Lincolnshire, and York¬ 
shire the families of Miliolidse, Astrorhizidse, and Lituolidse are 
represented by six genera and twelve species, the ma jority occurring 
plentifully. In these five specimens Ammodiscus incertus and Am. 
charoides occurred in every one, Ammodiscus gordialis in three, 
and Ammodiscus tenuis in two; species of Haplophragmium 
occur in all, one of which is new and seems peculiar to the North : 
it occurred in three out of the five specimens. Two species of 
Spiroloculina occur only in North-west Norfolk and Yorkshire. 
Reophax nodulosa is another form especially characteristic of 
this northern chalk. Only one specimen of Textularia was isolated, 
and three species of Bulimina , none of them common. The 
4219. x 2 
