60 EXTINCT MONSTERS. 
The Plesiosaur presents, on the one hand, points of resem- 
blance to turtles and lizards,—on the other hand, to crocodiles, 
whales, and, according to some authorities, even the strange 
Ornithorhynchus. But it will be very long before its ancestry can 
be made known. In the mean time, we must put it in a place 
somewhere near the fish-lizards, and leave posterity to complete 
what has at present only been begun. It must, however, be 
borne in mind that some of the above resemblances are purely 
accidental, and not such as point to relationship. Because their 
flippers are like those of a whale, it does not mean that Plesiosaurs 
are related to modern whales. It only means that similar 
habits tend to produce accidental resemblances — just as the 
whales and porpoises, in their turn, resemble fishes. To make 
torpedoes go rapidly through the water, inventors have given 
them a fish-like shape ;—in the same way the early forms of 
mammals, from which whales are descended, gradually adapted 
themselves to a life in the water, and so became modified to 
some extent to the shapes of fishes. 
The Pliosaurs, above mentioned, are evidently relations, but 
with short necks instead of long ones. They had enormous 
heads and thick necks. Fine specimens of their huge jaws, 
paddle-bones, etc., may be seen at the end of the reptile-gallery 
at Cromwell Road. One of the skulls exhibited there is nearly 
six feet long, while a hind paddle measures upwards of six and a 
half feet in length, of which thirty-seven inches is taken up by 
the thigh-bone alone. The teeth at the end of the jaws are truly 
enormous. One tooth, from a deposit known as the Kimmeridge 
Clay, is nearly a foot long from the tip of the crown to the base of 
the root. In some, the two jaw-bones of the lower jaw are partly 
united, as in the sperm-whale or cachalot. Creatures so armed 
must have been very destructive. 
