72 THK GEOLOGICAL HISTORY OF THE HORSE. 
are but very few fossils imbedded in it, yet small fossil fish are 
numerous towards the upper part of this bed : parts of the stems 
of trees are occasionally found, but they are completely filled up 
with silica. Now, as these could not have grown in the ocean, 
they must have become imbedded in this mass by other circum- 
stances, probably volcanic action. The great masses of rock salt 
in this country are also found in this formation, which is a com- 
plete proof of its marine origin, and most probably those depo- 
sitions and incrustations took place during the gradual decrease of 
the oceanic waters. 
The author assumes that the temperature now increased in 
warmth, since in the lias formation, which succeeds the new red 
sandstone, the remains of crocodiles, icthyosaurus, and plesiosau- 
rus, are found for the first time, with large nautilus ; and am- 
monites of a great variety of species, with a vast abundance of 
fishes covered with scales, an infinite variety of shell fish, Crustacea 
and testacea. Corals are also abundant in this bed. 
Immediately above this, in the marlstone beds, he traces the im- 
pressions of plants, most of which resemble those of the southern 
tropics of the present day. Again a change, and the oceanic 
waters preponderate. In the lower oolite the fossils are princi- 
pally marine, and perhaps these lived under a colder clime ; but 
the fossil remains are now so numerous and intermixed, that 
Mr. Saull cannot discover those broad and well-marked lines of 
distinction which he has so clearly pointed out heretofore. 
The coral rag exhibits an amazing growth of corals, many of 
them of the species growing at the present day in tropical seas. 
In the upper oolite he finds evidences of a warm climate, with 
its corresponding fossils ; the most remarkable of which are those 
resembling the zamia or Cycadeoidea of the present forests of Africa, 
with large fossil trees. Again, we arrive at fresh water and 
mixed beds, in one of which, the Wealden, are found the remains 
of the Iguanodon, so admirably described by Dr. Mantell. This 
amphibious reptile must have been, when at full growth, not less 
than eighty feet in length. Mr. Saull’s museum is rich in the 
number of bones it contains of this most extraordinary being. 
There are vertebrae resembling those of a fish, more than eight 
inches in diameter ; portions of the femur larger than those of 
the elephant of the present day; one immense claw, weighing 
nearly three pounds ; and several pelvis, and metatarsal, and meta- 
carpal bones, with many others. 
In the green sand, and in the gault, he is of opinion that the 
climate was again cooler ; but in the next beds, the chalk, the 
temperature unquestionably was hot; the fossils, and even the 
strata itself, being entirely of marine origin. 
At the period of the London clay, he supposes the waters gradu- 
