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FOSSIL REPTILIA OF THE 



expanded distal extremities of the unquestionable iscliia in Omosaurus. But such union 

 does not exist in Birds. If it should be found in all Dinosauria, it is one of the majority 

 of characters in which that order differs from the class of Birds and agrees with its own 

 class, viz. the Reptiles. 



Of the comparatively few sacral vertebrae in Dinosauria the ' costal portions of the trans- 

 verse processes' (pleurapophyses) abut chiefly against the part of the ilium contributing to the 

 cup to be upborne by the thigh-bone ; there are no postacetabular abutments against other 

 parts of the ilia, or against the comparatively broad ischia, as in Birds. In the latter pelvic 

 character we have again to quit the Reptilian class and to indicate the repetition of 

 it in certain bird-like Lissencephalous Mammals. 1 



The augmentation of number of sacral vertebrae beyond that — two — in Crocodiles and 

 Lizards, whose bellies trail upon the ground or are but little raised therefrom by the out- 

 sprawling fore and hind limbs in running along, relates in Land-tortoises to a more 

 vertical position of the leg, and to the greater weight which the entire hind limb has to 

 sustain in the progression of those Reptiles. 



In Dinosaurs (woodcut, Fig. 12) the thigh ( /), as well as the leg (tb), were probably less 

 obliquely disposed, in quadrupedal locomotion, than in any existing Reptiles, save, perhaps, 

 the Chameleons. The four or five sacrals, interlocked, as in Birds and Tortoises, by 

 alternating centrums and neural arches, have been recognised as physiologically related to 

 correspondingly developed hind-limbs and a concomitant carriage of their huge elongate 

 trunk, in a way approaching to that in the large gravigrade Mammals. 2 



It is requisite, in the present test, to determine as nearly as may be the relative length 

 of the pre-pelvic part of the trunk to the pelvis in Dinosaurs. 



It may be presumed that those who represent the pubic-ischial elements of such 

 pelvis, as being disposed in the avian fashion, intend the inference that, so far, the 

 pelvis of the Dinosaurs related to the same bipedal mode of progression as in Birds, 

 and that the trunk was similarly borne along, prone, upon the single pair of hind- 

 legs. 3 



If, however, our knowledge of the dinosaurian pelvis being rectified, it should be 

 averred that the trunk of the Iguanodon or Megalosaur might be otherwise carried than 

 in Birds, that it was reared upright and so balanced, as in Man, upon a pair of hind, 

 or in that case lower limbs, it may then be necessary to enter upon a series of comparisons 

 between the dinosaurian and human skeletons in connection with such upright mode of 

 progression. 



1 'Anat. of Vertebrates,' ii, pp. 397—402, figs. 263, 264, 266—268. 



2 'Report on Brit. Foss. Reptiles,' 1841. 



3 " Not a ground-crawler, like the alligator, but moving with free steps chiefly, if not solely, on the 

 hind limbs, and claiming a curious analogy, if not some degree of affinity, with the ostrich." Phillips, 

 ' Geology of Oxford,' p. 196. Such an idea, if it ever 'suggested itself to my mind, was never expressed, 

 and must have been instantly dismissed through considerations akin to those detailed in the text. 



