378 
THE GEOLOGY OE MAIDSTONE. 
Et W. H. Bets^sted, Esq. 
{Contimied from page 341.) 
The lower mandible of a clnmjera — the first discovered in the Lower 
Greensand — is now in the collection of Sir Philip Egerton, who in- 
forms me it belongs to the species Ischyodus Agassizii. Since this 
discovery I have met with many more specimens, some of smaller size ; 
but, from the difficulty of extracting them from the stone, I have never 
succeeded in getting one so perfect. Several good specimens have been 
procured from the Lower Chalk at Burham. The chimsera approaches 
in form to the shark tribe, but it is far from being so ravenous in its 
disposition. Eecent species are found in the Arctic and in some of 
tlie European seas, and attaining the length of two or three feet. 
Being often taken in the company of the herrings in their migrations, 
it has thus gained the patronymic "y^f "king of the herrings." The 
mouth of this odd-looking fish is furnished with hard and undivided 
plates instead of teeth, four of which are placed on the upper and 
two on the lower jaw. 
Eossils are very rare in the succeeding " rugged flint layers," 
which have an average thickness of eight inches. 
The next stratum in the quarry to be noticed is the " grey has- 
sock " bed. This stone is of very good texture for building, and 
contains a small species of Belemnite, which I have not seen in 
in any other layer. Iq this hassock there runs a thin bed of minute 
polished pebbles about the size of a pin's head, of various colours, 
and with them are mixed a profusion of small sharp-pointed fish-teeth. 
This accumulation appears to have been the result of a partial cur- 
rent, which carried away the small sand, leaving the larger pebbles as 
described. A species of Siphonia occurs in large quantities, marking 
the hassock with dark-grey wavy lines, but the stems are seldom dis- 
tinct enough to be extracted from the stone. 
There next follows a concretional layer, in which fossils rarely 
occur ; then a soft hassock ; and then a lower moUuskite bed, similar 
to the upper one, with fossils. 
" Soft hassock, No. 13," is a group of three layers of blue limestone, 
with two beds of hassock, having a total thickness of six feet. The 
group occupies a vertical space of about six feet. The shells found 
are peculiar to these beds, occurring only in them ; and there is also 
an immense accumulation of detached spicule — the remains of dead 
sponges. It is in this group that the Scaphite makes its first general 
appearance, one specimen only having been met with higher in the 
series (in layer No. 2), but I have not been able to decide if that be- 
longs to the same species. 
This is followed by "soft limestone;" and to this, again, succeeds 
a second bed of "soft hassock" (No. 14) which presents us with a 
very large species of fucus or siphonia, in great profusion. It is 
