412 
DR. G. J. HINDE ON BEDS OF SPONGE-REMAINS IN THE 
principally to the tetractinellidse and lithistidse. I did not find in any of the beds a 
single example or even the cast of an entire sponge. 
The sponge-beds appear not to continue with any regularity in a horizontal direc¬ 
tion, and they vary also in their characters in short distances. Thus the beds in the 
cliff section to the west of the harbour, though only imperfectly shown, are thicker, 
and decidedly contain more chert than those of the section described. This fact has 
already been noticed by Dr. Fitton* in the detailed sections which he has given of 
the various exposures round Folkestone. The same author describes very faithfully 
the peculiar characters of the sponge-beds, but, strange to say, he does not seem to 
have noticed the sponge-spicules in them. Mention is indeed made of siliceous 
spongy or spongiform concretions, but it is clear from the context that reference is 
only made to the peculiar porous nature of the deposits. They are also compared to 
the concretionary whetstones in the upper greensand of the Blackdown Hills in 
Devonshire, which latter, as will be shown in the sequel, are likewise sponge-beds. 
Isle of Wight. —Notwithstanding the thickness of the lower greensand strata in 
the Isle of Wight, sponge-remains do not appear to be present in them. 
Faringdon, Berkshire .—Though somewhat beyond the area of which this paper 
treats, it is desirable to make a brief mention of the remarkable deposit at this place, 
which has long been known under the name of the “ sponge gravel."’ The character 
of its deposition, and the nature of the sponges in it are altogether different from 
those of the beds of the same geological horizon in the Wealden area. It is a thick 
bed of unconsolidated quartz-sand and pebbles, with numerous sponges and other 
fossils. Sponges predominate, and they are present in astonishing profusion. They 
differ from those of the lower greensand of the Wealden area, not only in retaining 
their complete entire forms, but in the fact that they are exclusively calcisponges. 
Not a single siliceous sponge has as yet to my knowledge been met with in this 
gravel, though these calcisponges have been described by various authors as originally 
siliceous. They thus present a striking contrast to the sponge-beds in other areas, in 
which the sponges have been entirely disintegrated, and are also exclusively of 
siliceous origin. 
Sponge-Beds of the Upper Greensand. 
Accepting as a typical section that shown in the Undercliff of the Isle of Wight, I 
propose to include in this term the strata there present between the base of the 
so-called chloritic marl and the blue micaceous sands, which, in common with Captain 
IbbetsonI and Mr. Parkinson, ;{; I regard as the upper portion of the gault. Thus 
* “ Strata below the Chalk,” p. 116, et seq. 
t ‘ Notes on the Geology and Chemical Composition of the Various Strata in the Isle of A iglit, 
London. 1849. 
f Quart. Joui'n. Geol. Soc., vol. xxxvii., 1881, p. 375. 
