LOWER AND UPPER GREENSAND OF THE SOUTH OF ENGLAND. 
423 
the sections of the upper greensand at these places, but according to Mr. C. J. A. 
Meyer,'" there is one bed (No. 6 ) of a light-coloured sand, with chert in nodules or 
layers, varying from 7 to 25 feet ( 2’1 to 7 ‘5 m.) in thickness, which is crowded with 
sponge-spicules. Dr. BarroisI places this bed on the same geological horizon as the 
Blackdown deposits, but Mr. Meyer believes it to be above these latter. 
Sponge-beds in deposits of corresponding age in Germany, France, and Belgium. 
The general distribution of beds of sponge-remains in the lower and upper green¬ 
sands of the south of England would of itself furnish a strong probability that similar 
beds might also occur in the same formations on the Continent. This has already 
been shown to be the case with respect to the Hils-sandstein in Westphalia, and I am 
enabled to bring forward some evidence of the presence of sponge-beds in strata of 
cenomanian age in France and Belgium. 
Hils-sandstein, Westphalia. —This formation, which has a thickness of 150 m. 
(492 feet), was, until 1879, believed to be an ordinary sandstone composed of quartz- 
sand and mica cemented by silica. It was then stated by Herr Wgeckener | to be 
largely composed of huge sponges of irregular form, but Professor Zittel § showed 
that the supposed sponges were in reality nodular masses of rock filled with sponge- 
spicules or their casts, and that this rock was of organic origin and filled with the 
remains of sponges which lived on a sandy sea-bottom. The character of the rock 
very closely resembles the sponge-beds of Haslemere, and the formation is on the 
same geological horizon as the lower greensand. 
France and Belgium. —The description given by Dr. Charles Barrois|| of the 
petrological characters of the so-called gaize de TArgonne corresponded so exactly 
with the characters of the sponge-becls in the upper greensand that, in default of an 
opportunity of seeing this rock in situ, I applied to Dr. Barrois to furnish me with 
hand-specimens of it. My request was most kindly complied with, and the specimens 
which Dr. Barrois supplied to me from different localities fully confirmed the antici¬ 
pations which I had formed that the gaize was of organic origin, and largely composed 
of the remains of sponges. The specimens were obtained from the following localities, 
and I append short descriptions of their characters :— 
(1.) Grand Pre, Ardennes. —The gaize is a gray or grayish-yellow rock with bluish 
spots, soft to the feel, friable, and very porous. It appears to be principally of amor- 
* Quart. Journ. Geol. See., vol. xxx., 1874, p. 373. 
t ‘ Reclierches sur le terrain cretace de l’Angleterre,’ p. 70. 
+ ' Zeitschrift der deutschen geologischen Gesellschaft,’ vol. xxxi., 1879, p. 663. 
§ Id., p. 786. 
|| ‘ Annales de la Societe Geologique du Nord,’ tome v., 1877-78, p. 153. Tlie author says, “ Cette 
gaize est une roche teudre, legere, argileuse et silicieuse, tres poreuse; elle se delite a Lair avec la plus 
grande facilite; sa couleur est grise; elle contient cinquante pour cent de silice gelatineuse.” 
3 I 2 
