COERESPO^fDENCE. 
rose to the surface of the water, leaving the shell on the bed of the 
stream. As the dead bodies floated down the current the heads of 
islands, masses of fixed drifted wood, and the shores in many places 
were covered with them, tainting the air with putrid elfluvia.' " 
Now, nearly the whole of the shells which occur in this bed of rag- 
stone appear to have been dead shells. I mean, that from the open 
state of the valves it is probable that the animals were for the most part 
dead before they were enveloped in the sand and mud ; and from the 
large quantity of waterworn (coniferous) wood perforated by litho- 
domi, that is imbedded with them, it would appear that this stratum 
had constituted a bank of drifted wood and shells, presenting a very 
analogous condition to the phenomena above described. The mol- 
luscous bodies of the trigonias, gervillias, rostellarias, and oysters, 
etc., detached from their shells, would have been intermingled with 
drift-wood on such a sandbank ; while, in other cases, the animal- 
matter would remain in the shells. These masses becoming fos- 
silized would present when loose the patches of moUuskite, and when 
retained in the shells the phosphatic casts observed. 
The Eev. J. B. Keade submitted some of the molluskite to an ana- 
lysis by Mr. Eigg, who confirmed Dr. Mantell's suspicion of the 
presence of animal-carbon in it, and states that the darker portion 
of the substance contains about 35 per cent, of its weight. Dr. 
Mantell adds that a microscopical examination of some specimens 
with a low power detects innumerable portions of the nacreous la- 
minae of shells of extreme thinness, intermingled with carbonaceous 
matter, together with many siliceous spiculae of sponges, very minute 
spines of Echinodermata and Polypifera. Of these extraneous 
bodies he remarks, that probably they became intermingled in the 
soft animal-mass before the latter had undergone complete decom- 
position. He proposed the term Molluskite for this fossil sub- 
stance, and considers the substance of the dark spots and markings 
in the Purbeck marble to be identical. Since this paper was read, 
I have closely examined many of these bodies, and from the presence 
of minute bones of fishes, I am convinced that a very large proportion 
are the egesta of fishes. 
{To be continued.) 
COEEESPOKDENCE. 
TJie Mushliam Skull. 
Sir, — Have the following facts, stated by an anatomist of European re- 
putation for the last thirty years, any bearing on the question of the obli- 
quity foramen magnum in the Muskham skull, as described by Prof. 
Huxley and Mr. C. Carter Blake, in the ' Geologist' for June last ? 
Speaking of the Xaffirs, Dr. Knox states (' Paces of Men,' p. 226), that 
** the form of the skull differs from ours, and it is placed differently on 
