DINOSA URS. 



465 



series of forms, from those which walked aliout on all fours to those wliich stood 

 erect, an instance of evolution i)aralleleil in Manunalia. 



The first rei)resentatives to receive treatment will be those which had the jiroximal 

 tarsal hones separate from each other and raovably articulated to the terminal faces of 

 the tibia and fibula. Ilmlrosdurus had the teeth in several rows, and so juxtajjosed as 

 to give a pavement-like ai)i)earance to the armature of the jaw. The members of this 

 genus were of gigantic size, being twentj'-eight feet in length, the thigh-bone alone 

 having been forty inches long, though the humerus was only about one half this length. 

 The animals wandered through the old American forests and used their small fore 

 limbs to grasp the branches of trees and direct them to the mouth. In water as well 

 as on land they were active. 



Closely allied to the previous reptiles, though having the teeth in a single row, was 

 the Iguanodoii of the European Jurassic, an animal j)resenting many points of structure 

 in common with the iguana of to-day. Especially iguana-like were the peculiar teeth. 

 Though in the several museums of 

 Europe there are many fossil rep- 

 resentatives of this genus, the skel- 

 eton of /. liernissartensis, lately 

 found in Belgium, and now in the 

 possession of the Brussels museum, 

 is by far the most perfect, there 

 being but a few fragments missing. 

 The animal walked on its hind 

 limbs, as do the birds, and left in 

 the "Wealden strata its three-toed 

 tracks. The fore limbs, as will be 

 seen from the figure, were extreme- 

 ly short, and, besides being used 

 in gathering food, were probaljly 

 organs of defence, the thumi) be- 

 ing covered with a strong, conical spine, whicli could have pierced through the 

 body-walls of any animal which might unwittingly lead an .attack. When stand- 

 ing up, as it did while feeding, the Iguanodon had a stature of fourteen feet, though 

 when stretched out in the water, its broad tail acting as a propeller, it probably was 

 twenty-eight feet in length. Scelidosaurus differed from the Ljuanodou in having 

 four digits on its hind feet, though its teeth were in a single row. Specimens are 

 very uncommon. 



In 1878 what was then the largest known land animal was described by Professor 

 Cope as the Camarasaurus siqjremus, a reptile having the fore and hind limbs well 

 developed, the femur alone being six feet in height, and the animal having a total 

 length — including the strong and elongated tail — of about eighty feet. One of the 

 dorsal vertebra; measured over three feet in width, and equalled in size those of the 

 right whale. Such a huge rejjtile wandered about on the shores, or in the shallow 

 water, where it could easily reach to the tops of the larger shrubs, or, by resting on its 

 haunches, it might l)rowse on the tops of trees. It held its own, as a fossil, without a 

 rival, for only a short time, for soon, from the same deposit, the early cretaceous of 

 Dakota, appeared the bones of an allied animal, but differing in having the vertebral 

 centra strongly biconcave, or amphico^Ious, a pecidiarity which gave origin to the 



VOL. HI. —30 



utmtiKm 



Fig. 2G8. — Iguanodon bernissartensis, as restored by Dollo. 



