566 



MANUAL OF ZOOLOGY. 



intermediate in their characters between the Struthious Birds 

 and the typical Reptiles; whilst they have been supposed to 

 have affinities to the Pachydermatous Mammals. Most of the 

 Dinosauria were of gigantic size, and the order is defined by 

 the following characters : 



The skin was sometimes naked, sometimes furnished with a 



well - developed exo skeleton , 

 consisting of bony shields, 

 much resembling those of 

 the Crocodiles. A few of 

 the anterior vertebra were 

 opisthocozlous , the remainder 

 having flat or slightly bi- 

 concave bodies. The ante- 

 rior trunk-ribs were double- 

 headed. The teeth were con- 

 flned to the jaws and im- 

 planted in distinct sockets. 

 There were always two 

 pairs of limbs, and these 

 were strong, furnished with 

 claws, and adapted for ter- 

 restrial progression. In 

 some cases the fore -limbs 

 were very small in propor- 

 tion to the size of the hind- 

 limbs. No clavicles have 

 been discovered. 



The teeth are sometimes 

 implanted in distinct sock- 

 ets, and they are never 

 anchylosed with the jaws. 



Fig. 318. Leg of Deinosaur. il Ilium ; is 

 Ischium ; f Femur ; t Tibia ; j Fibula ; as 



Astragalus ; ca Calcaneum ; m Metatarsus. 

 (After Huxley.) 



are much elongated; the 

 inner wall of the acetab- 

 ulum is formed by mem- 

 brane; the tibia has its proximal end prolonged anteriorly 

 into a strong crest ; and the astragalus is bird-like (Huxley). 



The most remarkable points in the organisation of the 

 Dinosauria are connected with the structure of the pelvis 

 and hind-limb, the characters of which, as pointed out by 

 Huxley, approximate to those of the same parts in the Birds, 

 and especially in the Struthious Birds. This approximation 

 is especially seen in the prolongation of the ilium in front of 

 the acetabulum (fig. 318), the elongation and slenderness of 



