384 
YERTEBRATA. 
THE MEGALOSArETJS AND PTERODACTTLES. 
Tlie Hylceosauriis was anotlier enormous reptile, whose remains were found in tLe wealden* 
of Tilgate Forest. This animal appears to haye combined some of the features both of the croco- 
dile and of the lizard. It was covered with thick scales, and along the back was a row of 
long conical bones or spines, resembling the crests we have described as belonging to the Iguanas 
and Agamas. This animal is supposed to have been a terrestrial, herbivorous reptile, between 
twenty and thirty feet in length. Altogether it must have been of the most extraordinary rep- 
tilian organization. 
The Megalosaurus was another gigantic lizard, whose remains have been found in the same 
localities as the preceding. From the teeth, of which numerous specimens have been discovered, 
and which had a conical, saber-like form, it is inferred that the animal was carnivorous. It was 
probably twenty-five to thirty feet long. 
The Plesiosaurus we have already described (page 8, vol. I.) ; of the Ichthyosaurus there were 
many species. " These," says Mantell, "had the beak of a porpoise, the teeth of a crocodile, the 
head and sternum of a lizard, the paddles of a cetacea, and the vertebra3 of a fish." Some of the 
species were of the size of young whales. The bones forming the sternum, or chest resemble 
those of the omithorhynchus ; the paddles are four, and are like those of the turtles. In some 
species the bones of the fore-paddles are one hundred in number. The general form was like that 
of the gTampus. The skin was destitute of scales. It was evidently carnivorous and aquatic. 
* Wealden is a term used by English geologists in application to the uppermost series of the strata included in 
what is called the Oolitic sygtem, that is, the rocks of the secondary formation, of which the Bath stone and Portland 
stone of England are examples. The term weaMe7i v^aa adopted from the fact that the formation was first ob.served 
in the wealds, that is, woods, of Sussex and Kent, in England. The Tilgate Forests are a part of this region. The 
whole consists of limestone, conglomerate, sandstone, and clay, abounding in the remains of fresh-water and land 
animals. These are supposed to have been deposited in an estuary or arm of the sea, which once covered this part 
of England. 
