LOWER AND UPPER GREENSAND OF THE SOUTH OF ENGLAND. 439 
15. Body-acerates of Geodites (Plate 41, figs. IO-IOo).—S traight, curved, or genic¬ 
ulate fusiform spicules, either acutely pointed or obtuse. The canals are only preserved 
as a rule in the spicules from Warminster and Merstham, in which the colloidal silica 
remains unaltered. The spicules vary from IT to 3'12 ram. in length, and from '04 to 
T25 mm. in width. These spicules are very generally distributed in all the sponge- 
beds alike of the lower and upper greensand. The larger forms occur in the lower 
greensand of Haslemere, Sevenoaks, and Folkestone, and in the upper greensand of 
Blackdown and Haldon ; whilst those from Warminster and the malm at Merstham 
are distinctly smaller forms. 
16. Pachymatismci virga (Plate 41, figs. 15, 15a, 16).—Straight, slender, cylindrical 
spicules, terminating obtusely, occasionally also slightly inflated. Length P6 to 
2 mm.,, by '025 to '041 mm. in width. With these there also occurs an inequally 
biclavate spicule (fig. 16), IT6 mm. in length, by '066 mm. in width. Dr. Bowerbank 
has figured spicules of similar form, but much slenderer proportions, in Pachymatismci 
Johnstonia (‘ Brit. Sponges/ vol. i., Plate 1, figs. 12, 20 ; vol. iii., Plate 8, figs. 2, 3), and 
I place these provisionally in the same genus. 
U. G. S., Blackdown, Haldon. 
17. Geodites Ccirteri (Plate 41, figs. 17-17&).—-Zone spicules, with straight or slightly 
curved shafts, gradually tapering from the head, terminating obtusely. The rays 
straight or slightly curved, simple or furcate, acutely pointed, projecting forwards. 
In some forms one of the rays is suppressed and the spicule resembles a two-pronged 
fork (l 7b, k). The rays are frequently inequal in length, and bifurcate irregularly. 
Total length 1'4 to 1'75 mm., by 7 to 75 mm. in width; the rays '375 to '45 mm. 
in length, by 7 mm. wide. Abundant. 
L. G. S., Haslemere, Tilburstow Hill, Sevenoaks (Folkestone division). U. G. S., 
Blackdown, Haldon. 
18. Geoditesprcelongus (Plate 42, figs. 1-lc).—Zone spicules, with elongated, nearly 
straight shafts, of nearly the same width throughout, or very gradually tapering. 
'Ihe head-ravs are relatively short, simple, or bifurcate, usually slightly curved. They 
project obliquely forwards. Total length from 1'9 to 3'42 mm. ; width, from 713 to 
75 mm. The rays are from 775 to '425 mm. in length, by '075 mm. in width. 
L. G. S., Haslemere, Tilburstow Hill, Folkestone, Sevenoaks. U. G. S., Blackdown. 
19. Geodites robustus (Plate 42, figs. 42, 2a).—Zone spicules robust, straight or 
slightly curved, tapering gradually, or of the same thickness for the greater part 
of their length. Bays also stout, simple, or bifurcate, projecting obliquely. Length 
2 - 8 to 3'3 mm., width, 77 to '3 mm. The rays are from '25 to '45 mm. in 
length, by 71 to 75 mm. in thickness. Differs from the preceding form in being 
more robust throughout, and in the greater development of the rays. 
L. G. S., Haslemere, Tilburstow Hill, Sevenoaks, Folkestone. 
20. Geodites audax (Plate 42, figs. 3-3c).—Zone spicules robust, the shaft usually 
with a slight constriction just beneath the head, then gradually tapering to an acute 
3 L 2 
