302 Dr. F. A. Bather—A Cidarid from Hartwell. 
Whichever theory is held, there is always the difficulty of the 
gap between the undoubted estuarine deposits of France and the 
English freshwater beds on the one side, and the marine deposits of 
the. south on the other, and unless these gaps can be bridged it is 
doubtful whether any definite solution of the problem can be found. 
I have to thank Dr. H. H. Thomas for his kindness in looking at 
the slides and reading the manuscript. I have also to offer my 
thanks for being allowed to carry on this work at Bedford College; 
and especially to Miss Raisin for much help throughout the 
investigation. 
EXPLANATION OF PLATE XII. 
Fic. 
1. Heavy grains from Ashdown Sand of Forest Row (separated by heavy 
fluid, s.g. 83-0317), showing slender zircon crystals, one terminated by 
a pyramid at each end. x 60, approx. 
2. Heavy grains from Hastings Sand of Bexhill (separated by heavy fluid, 
s.g. 3-292), showing zircon crystal withinclusions. Crystal terminated 
at one end by pyramid faces and at the other probably by a basal plane. 
x 90, approx. 
3. Grains of Ashdown Sand from Forest Row, sinking in solution of mercuric 
potassium iodide (s.g. 3-0317), but floating on solution of cadmium 
borotungstate (s.g. 3-317), showing mainly tourmaline. 30, approx. _ 
4. Heavy grains from Tunbridge Wells Sand of Lindfield (separated by heavy 
fluid, s.g. 3-035), showing tabular crystal of anatase. x 85, approx. 
5. Heavy grains from Wealden Sand of Equihen (Boulonnais) (separated by 
heavy fluid, s.g. 3-035), showing kyanite with cleavages. x 80, approx. 
6. Section of conglomerate in Tunbridge Wells Sand from Lindfield, 
containing one small pebble of chert, showing structures which include 
one spiral organism. x 20, approx. 
III.—A Ciparr From tHE Harrwett Ciay. 
By F. A. BATHER, M.A., D.Sc., F.R.S. 
(Published by permission of the Trustees of the British Museum.) 
EMAINS of Echinoderms are so rare in the Hartwell Clay of 
Buckinghamshire, and when found so fragmentary, that it may 
be worth while drawing attention to a small piece of an Hchinoid 
test recently obtained from the Hartwell Brick-pit by Mr. Edwin 
Hollis, F.Z.S., curator of the Aylesbury Museum, and presented by 
him to the national collection (Brit. Mus., Geol. Dept., H12241). 
The terminology of the following description is that defined on 
pages 59-65 of my ‘‘ Triassic Echinoderms of Bakony”’, Budapest, 
1909. 
The fragment represents the greater part of two adjacent inter- 
ambulacral plates of a Cidarid. The portion missing is the adradial 
tract. It can be inferred from the faces of the transverse sutures 
that these plates come from the right-hand (or 4) column of the inter- 
ambulacrum. In the interradial suture-margin of each plate the 
apicad limb is about twice the length of the orad limb, whence it 
may be inferred that the plates come from above the ambitus. But 
since the height of the lower plate is slightly less than that of the 
upper, they cannot have been far above the ambitus. 
