LOWER. AND UPPER GREENSAND OF THE SOUTH OF ENGLAND. 
449 
Fig. 2. Microscopic section of a nodule from the upper greensand firestone at God- 
stone, filled with spicules of colloid silica in a siliceo-calcareous matrix. 
X 40 diameters. 
Fig. 3. Microscopic section of chert from the upper greensand at Penzlewood, showing 
spicules and spicular canals of chalcedonic and crystalline silica, in a matrix 
of the same material. X 40 diameters. 
Fig. 4. Microscopic section of a sponge-bed in the lower greensand at Tilburstow Hill, 
showing spicules replaced by crystalline calcite, inclosed in a matrix of 
granular calcite. X 40 diameters. 
Fig. 5. Microscopic section of the malm rock from Merstham, showing a portion of a 
sponge-spicule in which the silica is in the globular form. The matrix 
largely consists also of colloid globular silica, with mica scales, grains of 
glauconite, and a small proportion of chalcedonic silica. X 150 diameters. 
Fig. 6. Microscopic section of a spongedaed in the upper greensand at Warminster, 
. showing a portion of a sponge-spicule, the central part of which consists 
of colloid silica in a globular form, whilst the exterior is of chalcedonic 
silica. X 150 diameters. 
Fig. 7. A fractured surface of the upper greensand “ malm ” at Merstham, showing 
the empty casts of spicules in a matrix of globular silica. X 40 diameters. 
Fig. 8. A portion of a sponge-spicule from Warminster, in which the colloid silica is 
traversed by curved lines. X 150 diameters. 
Fig. 9. A microscopic section of a portion of another spicule, still further magnified, 
in which the lines appear as incomplete elliptical rings with smooth rims. 
X 560 diameters. 
PLATE 41. 
Figs. 1, la, b. Reniera gracilis. —Haslemere, Blackdown. X 60 diameters. 
Figs. 2, 2a. Reniera obtusa. —Blackdown. X 60 diameters. 
Figs. 3, 3a, b. Reniera cucumis. —Near Warminster. X 60 diameters. 
Figs. 4, Aa-e. Reniera Zitteli, Pocta. —Haslemere, Blackdown. X 60 diameters. 
Figs. 5, 5 a~f. Reniera truncata. —Near Warminster. X60 diameters. 
Figs. 5 g—h. Reniera truncata? Immature spicules in which the canal remains open 
throughout its length.—Near Warminster. X 60 diameters. 
Figs. 6, 6a-e. Axinella dispersa. —Blackdown ; near Warminster, Merstham. X 60 
diameters. 
Figs. 7, 7a. Axinella gracilis. —Haslemere, Blackdown. X 60 diameters. 
Figs. 8, 8 a-d. Axinella stylus. —Haslemere, Blackdown. X 40 diameters. 
Figs. 9, 9a. Spirastrella neocomiensis. —Haslemere. X 60 diameters. 
bigs. 10, 10a-o. Geodites. Acuate spicules of different forms and dimensions be¬ 
longing to various species.—Haslemere, Blackdown, Haldon; near War¬ 
minster, Merstham. X 40 diameters. 
