AFFIXITIES OF THE GEXES PE0T0SP0:NGIA. 363
after a study of the -whole of the material which has come under my
observation, I feel no difficulty in definitely assigning to Protosponrjia
its place amongst the other sponges. Moreover, as Dr. Hicks's figure
of his specimen is almost purely diagrammatic, I have ventured to
insert here a fresh drawing of part of it, kindly made for me by my
friend Mr. T. H. Thomas, of Cardiff. The great interest which must
necessaril.' attach to the best-preserved specimen of the oldest known
sponge renders excuse for this second representation of it needless.
3. Desceiptiox.
The specimens on which Salter's description was based were
crushed and flattened forms in which the skeleton appears as raised
lines or narrow thread-like ridges arranged in a lattice- like reticula-
tion on the bedding-planes of the slate which serves as a matrix.
Dr. Hicks's specimen (fig. 1), on the other hand, presents us with the
Fig. 1. — Part of tlie specimen 0/ Protospongia feuestrata, in the
IVoodwardian Mtrscmii. (.S'atural size.)
spicules of the sponge in their original form, unaltered, or but slightly
altered by pressure, and standing out in free relief from the weathered
matrix, which has in several places been artistically cleared away
from beneath them.
In this state of perfect preservation the spicules are clearly not
fused together into a continuous network ; they are separated and
free, and only form a network by the interlacing of their extremities.
Their form also is somewhat different from that of the s^ncules of
crushed specimens.
Form of tJie Sjncules. — Each sj^icule is quadriradiate, with its
centre raised some slight but variable distance above the plane in
which its rays terminate. Its general form may be most easily
described by imagining it as modelled upon a low four- sided pyra-