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FOSSIL KEPTILIA OF THE 



difficulty which the known structure and proportions of the trunk oppose to the bipedal 

 progression of Dinosauria ? 



Nothing of such exists in the length of the neck, nothing in the number or in the 

 freedom of flexibility in opposite directions of the cervical vertebrae ; on the contrary, those 

 vertebrae in Dinosauria which are anterior to the bearers of the long and free ribs are few 

 in number, with the little flexibility allowed by their reciprocal joints checked by the 

 disposition of their short and mostly imbricate ribs. The neck of the Dinosaur was 

 short, straight or nearly so, and strengthened by the overlapping pleurapophyses for the 



carriage of a massive head projecting forward almost in a line with the body : never 

 could such head be carried back, by a graceful sigmoid bend of a long neck, so as to be 

 poised above the centre of support afforded exclusively by a hind pair of limbs. 



Such head, with its powerful jaws and their dense and weighty dental armature, needed 

 the development and structure of a pair of fore-limbs, to sustain it with the fore part of 

 the trunk, and take the required share in bearing along the bulky dinosaurian quad- 

 ruped. Omosaurus adds a pregnant instance of the requisite anterior pair of supports. 

 What the Dinosaur needed for its mode of terrestrial locomotion the Bird has not ; 

 and what the Bird possesses for its mode of terrestrial locomotion the land Reptile is 

 devoid of. 



I have alluded to the modifications, extreme and beautiful they are, of the hind limb- 

 bones of the Bird for the functions concentrated therein ; the suppression, viz., of the tarsal 

 segment ; the simplification, unification, consolidation of the segments above and beneath 



