378 



THE GEOLOGY OE MAIDSTONE. 

 Et W, H. Bensted, Esq. 



(Continued from pa^e 341.) 



The lower mandible of a cbimsera — 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 chimasra 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 of "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 spiculae — 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 liave not been able to decide if that be- 

 longs to the same species. 



Tliis 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 



