434 
DR. G. J. HINDE ON BEDS OF SPONGE-REMAINS IN THE 
from each other in a more perfect manner than it is always possible to obtain those of 
recent sponges by artificial means. 
Spicules thus loosely imbedded have been met with in the lower greensand strata 
of Haslemere, Sevenoaks, and Tilburstow Hill, and from beds of upper greensand age 
in the vicinity of Warminster, Haldon, Blackdown, and Merstham. Figures are given 
in the accompanying plates of all the forms discovered ; some of these are of general 
distribution, whilst others are restricted to the deposits of a single locality. With 
the exception of the spicules from Haldon and Blackdown, first partly described by 
Mr. Parkitt,* and subsequently and more completely by Mr. Carter,, t this is the 
first time that those from the lower greensand and from the other localities above 
mentioned in the upper greensand strata have been figured in detail. 
Mention has already been made of the fact that the spicules of the sponge-beds 
referred to in this paper (the Faringdon sponge-gravel not being included) are 
exclusively those of sponges with siliceous skeletons. liepresentatives of each of the 
four orders of siliceous sponges occur, but in varying proportions. Monactinellid 
spicules of acerate, acuate, and cylindrical forms are very abundant, but, judging 
from their relative dimensions, the majority of these spicules belong to the tetracti- 
nellidse, where they are associated with trifid spicules, rather than to those monacti- 
nellids whose skeletons are exclusively composed of uniaxial spicules. It is quite 
possible, however, that monactinellid sponges may have been also numerous in these 
sponge-beds, though we have but few spicules which can be definitely recognised as 
belonging to this order, for the spicules of most of the recent monactinellids are so 
minute and delicate that they would most likely be destroyed in fossilisation. 
Tetractinellid sponges are strongly represented, and the majority of the spicules in the 
sponge-beds are included in this order. There is a, very great variety of the “ zone ” 
spicules of these sponges, each of which probably indicates a distinct species. The 
so-called “ anchor ” spicules, the globates and stello-globates, which form a dermal 
layer in some of these sponges, are also present. The lithistid sponges are princi¬ 
pally represented by spicules belonging to the megamorina family. These are very 
numerous and very generally distributed. The skeletal spicules of the other families 
of lithistids are less common, and their generally minute dimensions may partly 
account for this fact. There is, however, a great number of the dermal spicules of 
lithistid sponges, which most probably belong to the tetracladina family. These 
dermal spicules are but seldom preserved on the surface of the entire lithistid 
sponges which have been discovered in the greensand, but they are present, quite 
detached from each other, in the sponge-beds, in a great variety of forms. The 
remains of hexactinellid sponges are comparatively rare, and they are limited to 
small fragments of the mesh and a few detached spicules probably belonging to the 
surface layer of the sponge. 
* ‘ Transactions of the Devonshire Association for the Advancement of Science,’ 1870. 
t Ann. Mag. Nat. Hist., 1871, ser. 4, vol. vii., p. 113, pi. 7-10. 
