388 REPORT—1890. 
in fact, owes its formation to the existence of a hollow in the surface of 
the Gault, which is here only between 110 and 120 feet thick.”! 
The Polyzoa of the Gault, however, require working out, and in this 
report I am unable to give even a provisional list. 
PoLYZOA FROM THE CAMBRIDGE GREENSAND. 
For the classification of the Chalk rocks in the neighbourhood of Cam- 
bridge, a very useful ‘Table of Chalk Zones’ is arranged by Messrs. 
Penning and Jukes-Browne in the paper already quoted from (page 21). 
As a preface to the introduction to this ‘Table’ the authors remark: 
‘With regard to the larger divisions under which the succession of 
zones may be grouped, we have felt it desirable to revive the general 
classification proposed by Mr. 8S. Woodward, in 1833, for the Chalk of 
Norfolk. The Melbourn rock and the Chalk rock form such marked 
breaks in the series that it naturally falls into three main divisions— 
lower, middle, and upper. We may point out that these exactly corre- 
spond with those termed by d’Orbigny ‘“ Cénomanien,” ‘‘Turonien,” and 
“‘ Sénonien,” as they are defined by Dr. Barrois ’? (pp. 20-21). 
The only portion of the table that I shall quote is the section 
bracketed as Lower Chalk, for the purpose of showing the position of the 
Cambridge Greensand in the neighbourhood of Cambridge. 
cit Bedfordshire and Bucks. Cambridgeshire pipe eee us 
curved bedding; 60ft. | globosus; 80 ft. Zone of Holaster 
Totternhoe stone; 10—| Totternhoe Stone; 15 ft. subglobosus ; 
! Blocky Chalk, with) Zone of Holaster swb- 
15 ft. 150 ft. in three 
Cenomanian. 
pe Totternhoe Marl; 80ft.| Zone of Rhynchonella divisions. 
= z Martini; 50-60 ft. 
Ss || CAMBRIDGE GREEN- |? Chloritic Marl. 
SAND. 
I have already written two papers on the Polyzoa of the Cambridge 
Greensand,’ one in 1885, and the other in 1889. The material that I 
used for the purpose of those papers was derived from different 
places, and supplied to me by Mr. Jesson. One lot of material contained 
a large number of fragments of Polyzoa and other organisms, which were 
picked out from washings of the débris of the phosphate beds from 
the Coldham Lane pits. Nearly all the Polyzoan fragments from the 
phosphate beds were free, that is to say, they were unattached to any 
particular fossil. The other series of Polyzoa described by me from the 
Cambridge Greensand were in many respects similar to the first, but 
were attached to several large fossils, which were, I believe, peculiar to 
the Cambridge Greensand; and whatever doubt may be thrown out 
respecting the true horizon of the first set of forms, the same will not 
apply to the second set, and it was this last set only that I ventured 
1 Mem. Geol. Survey, Map 51 8.W.: ‘Geology of the Neighbourhood of Cam- 
bridge,’ p. 15. 
2 Recherches sur le Terr. Crét. supérieur de V Angleterre et de V Irlande, 1876. 
3 <Polyzoa of the Cambridge Greensand,’ Proc. Yorksh. Geol. and Polytech. Soc. 
vol. ix.; ‘Further Notes,’ &c. vol. xi. pt. ii. 
