380 
THE GEOLOGIST. 
The "Black Greys" (border) is one of the most remarkable of 
the whole series of beds displayed in the Iguanodon quarry. Its 
sandy border contains an immense accumulation of organic remains 
— all marine, with the exception of fragments of wood perforated by 
teredines, of which animals, in most cases, the sheaths remain. The 
sandstone is of a dark grey, hard and coarse in texture, and about 
twelve inches thick. A portion is full of the casts and markings of 
Siphoniffi and Fucils TargGnii. Casts of Trigonia alctformis are very 
abundant, and, as in the Molluskite layer, the shells are open, and 
of the dead mollusksthe carbonaceous matter is found in large quan- 
tities. At thfe junction of the hassock with the limestone beneath 
it, two beds containing shells in great profusion. The first contains 
chiefly the shells of a Panopea, but the substance of the shell is now 
nothing more than a slight film of lime, which falls to dust when dry. 
The difiiculty of getting specimens is also greatly increased by their 
crushed condition, being almost flattened by the pressure they have 
undergone. Immediately under this vein of shells, and sometimes 
mingling with them, is seen for the first time a bed of the charac- 
teristic Gryphsea, or Exogyra. These shells often occur in groups of 
considerable numbers, and I have had five good specimens within a 
thickness of stone not exceeding three inches. This bed of shells 
appears to have only existed for a short period, as the occurrence of 
an individual in any part of the remaining portion of the layer is 
rarely seen ; and, indeed, the stone is remarkably free from any re- 
mains of animal life. The accumulation of Siphonise gives the rough 
fracture so generally found in ragstone, but occasionally a smooth 
flat surface is obtained by cleavage. The hassock contains many 
nodules of clear blue limestone, very similar to septaria. This oc- 
currence in the coarse sandstone is remarkable, as the stone is of a 
very clear structure, light blue in colour, and in some instances of a 
pear-shaped figure, from which I attribute their origin to zoophytic 
structure, although no traces of such structure has been detected. 
Below the last-mentioned layer the stone is of inferior quality. The 
fossils are of the same kind as those occurring in the border of the 
" Black Greys." The only opportunity I have had of examining 
them was during the sinking of a well, when water was found at 
twelve feet below the "Black Greys." Detached spicule, Trigoniae, 
Plagiostomse, stems of Siphonise, Plicatulje, and Belemnites, were 
very abundant. The layers were as under : — 
Concretionary masses of greyish limestone, from 6 to ] 2 inches in thickness. 
Few fossils. 
Hard coarse hassock, 2 feet in thickness. Siphonise in large masses ; casts of 
Trigonia alceformis. 
Thin layer of stone. 
Soft hassock, about 6 inches, with spiculte. 
Grey-blue limestone of clear fracture. Few shells. 6 to 7 inches thick. 
Hard hassock, 18 inches. Impressions of Siphonise. 
Water was then found in loose rubbly layers of stone. 
Having now terminated the description of the series found in my 
