f)10 BRITISH FOSSIL REPTILES. 



The proportion of the skeleton of Cetiosaurus longus in the Oxford Museum and that 

 of the allied Dinosaur {Omosaurus armatus) in the British Museum demonstrate the absence 

 of anclulosis in the dorso-lumbar region of the spine, and of any of the modifications of 

 the hindmost vertebra) which, in Birds, add to the mechanical bracing of the trunk upon 

 the pelvis : they show no lengthened pleurapophyses, having free proximal articulations 

 to anterior sacral vertebrae ; but, on the contrary, as in Mammalian cpiadrupeds, the 

 lumbar ribs are short, coalesced with their vertebra, and project as straight out- 

 standing ti'ansverse processes, not opposing the lateral movements of the trunk upon the 

 pelvis, but, with the antecedent vertebra?, negativing the notion of any action of muscles, 

 proceeding from the pelvis and thigh-bones to grasp fast a trunk, and uplift it, together 

 with the fore-limbs, neck, and head, clear of the ground, as during the hypothetical 

 bipedal march and course of the huge dinosaurian Reptiles. 



The ascertained conformity of organisation in known Dinosauria supports the 

 conclusion that a long, bulky, bendible body stretched forward from the pelvis and hind 

 limbs throughout the order. 



In Birds the bony ' vertebral ' and ' sternal ' ribs of the few vertebras of their short 

 dorsal region are spliced together by a mechanism of which no trace has hitherto been 

 discovered in the corresponding more lengthened region of the spine of Dinosauria ; there 

 is a like absence, in these cold-blooded vertebrates, of the anchylosis of centrums, and of 

 ossified tendons or neurapophysial splints — avian structures — which limit, to the essential 

 minimum, any movement between one prepelvic vertebra and another. Every modifica- 

 tion of the Bird's skeleton concurs to facilitate the carriage of the prone trunk, as one 

 compacted mass, upon the vertical pair of limbs, and not one of these modifications exists 

 in Reptiles recent or extinct. 



What, then, ive next ask, were the arrangements in the neck to din.;inish 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 \vith 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-hmbs, 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. 



