LOWER CHALK—MICROGRAPHIC STRUCTURE. 
287 
seen in southern samples, and Spiroloculinaaspenda. Species of Text¬ 
ularia, abundant in the south, are here absent, with the exception 
of Textularia trochus; Bulimina too is comparatively rare, though 
a few of the commoner varieties occurred ; Haplophragmium acuti- 
dorsatum was found in every sample of this zone at Speeton, but 
was not noticed in the south; and Gaudryina filiformis and Gau¬ 
dryina 'pupoides (common in the south) are rare at Speeton. 
|# Of the forms which occurred most commonly in the acid resi¬ 
dues of this zone in the southern and western counties, the most 
abundant were Bulimina Presli and its variety sabulosa, with 
Bulimina brevis, B. obtusa, and B. affinis. Gaudryina pupoides 
was very common in every southern sample, Tritaxia tricarinata 
occurred in every sample, and Tritaxia pyramidata w T as also fre¬ 
quently noted, but neither species occurred in Norfolk and to the 
north of the Wash. Of the genus Textularia, Textularia trochus 
and Textularia turris were most regular in their occurrence, Textu¬ 
laria prelonga and Textularia minuta being next in order of fre¬ 
quency. Ammodiscus incertus, though occurring in the upper 
part of the zone at Folkestone and Arlesey was by no means common. 
Portions of the test of Reophax, built of very coarse particles of sand, 
were common in the acid residues of samples of this zone from 
Mupe Bay, especially in the lower part of it, and a few of similar 
character were found in the base of the zone at the Isle of Wight. 
The two species of Spiroplecta again occurred in the Dorset speci¬ 
mens, and were not noticed in those to the eastward. 
The whole of the Lagenidae, Globigerinidae and Rotaliidae were 
obtained from four specimens of the zone taken from the fol¬ 
lowing localities: Folkestone, Charlton cutting on the Midland 
Railway (a few miles north of Luton), Arlesey in Bedfordshire, 
and Barrington in Cambridgeshire. In the first and last of 
these localities the specimens came from the base of the zone; 
those from Charlton and Arlesey, near the top of it. The species of 
these families seemed fairly distributed throughout the deposit, 
and it cannot be said that any particular part of the zone was espe¬ 
cially characterised by the occurrence of any one form or forms. 
Gristellaria gaultina was the most common form of the family 
Lagenidae, Gristellaria planiuscula coming next in the regularity 
of its occurrence. Rhabdogonium excavatum, Marginulina glabra , 
Polymorphina fusiformis, and Ramulina aculeata occurred in all 
specimens from the above-named localities. Globigerina cretacea 
were common ; the tests, though fairly large, are not so fine as those 
of the Middle Chalk. Of the Rotaliidae, Anomalina avimonoides 
and Rotalia Soldani were most frequent in occurrence. 
Ostracoda. — The valves of Ostracods are very abundant in some 
specimens of the chalk of this zone; they were especially so in the 
specimen from 10 feet above the Cambridge Creensand at Bar¬ 
rington, Cambridgeshire. The following is a list of those species 
isolated which were examined and identified by Mr. Chapman. 
