Bt IDS = 
whilst the larger attain dimensions of 5,5 mm. in length by 
0,135 mm. in width. Occasionally spicules of still larger di- 
mensions are present; one of these, though incomplete at 
one end, measured 9,2 mm. long by 0,214 mm. wide; a frag- 
ment of another was 0,35 mm. in diameter. 
There are also straight and curved spicules (figs. 8, 9) 
facsimiles of the larger spicules as regards their form but 
very much smaller. The straight forms of these small exam- 
ples average 1,35 mm. long by 0,022 mm. wide, whilst the 
curved, shorter and proportionally stouter, average 0,585 mm. 
in length by 0,067 mm. in width. These curved spicules are 
abruptly pointed at both ends and very constant in form and 
size. Both the larger and smaller forms are abundant in the 
flint meal. 
Simple acerate spicules are common to so many different 
forms of sponges that it is impossible to determine the rela- 
tions of detached spicules with certainty, but, judging from 
the size of those in this deposit, they appear to me to cor- 
respond rather with acerates which in existing sponges are 
associated with the trifid spicules of Geodia and Stelletta 
than with the acerates of monactinellid sponges. Similar 
spicules are described by Mr. Carter from the Haldon Green 
Sand and referred to Geodia- like sponges (An. Mag. Nat. 
Fist. Seq) Veli :7,.p. ‘p20; Pleo; figs 75,7 0)} they ane 
present in the Upper Chalk of Coesfeld (Ueber Coelop. p. 36, 
Taf. IV, figs. 1—4) in the Chalk of the North of Ireland 
(Wright: op cit. Plate II, fig. 1) and also in the Eocene sand 
of Brussels (Rutot, op. cit. Pl. III, figs. 1—4). 
Ophiraphidites, sp. 
(Plate I, figs. 6—9). 
Acerate spicules gradually tapering from the centre to 
either end; sinuous and curved in a great variety of forms. 
Some specimens have the main portion of the spicule nearly 
straight and the extremities abruptly bent in opposite direc- 
