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FOSSIL REPTILIA OF THE 



tuting the alleged inaccurate characters of the reptilian group Dinosauria. If I have to 

 offer, in relation to the main end and aim of my labours, any remark which may seem 

 critical, it will be accompanied by its grounds. Thus, in regard to the characters pro- 

 posed by Professor Huxley for the Order Dinosauria — 



"1. The dorsal vertebras have amphiccelous or opisthoccelous centra. They are pro- 

 vided with capitular and tubercular transverse processes, the latter being much the 

 longer" (loc. cit., p. 33). 



If by ' amphiccelous' be meant ' biconcave,' as the term ' amphiccelian' has been 

 applied to dorsal vertebras of the Ichthyosaurus, no such vertebrae exist in the dorsal 

 region of Dinosauria. The term ' amphiplatyan' would more truly express the configura- 

 tion of the terminal articular surfaces of the centrum in such dorsal vertebras as are figured 

 in Pis. XII and XIII of the present ' Monograph,' and in corresponding vertebras of Igua- 

 nodon Meyalosaurus, Cetiosaurus, Hylaosaurus, Scelidosaurus, Bothriospondylus, figured in 

 previous Monographs on British Fossil Dinosaurs. Not that the flatness of both ends of 

 the centrum is absolute, but the deviation is slight and usually, when in the direction of 

 concavity, confined to the hinder surface. Neither must it be supposed that the dorsal 

 series may be ' amphiccelous' in one Dinosaur, or ' opisthoccelous' in another. 



The centrum in some Dinosaurs, Tapinocephalus, e. g., shows at the middle of its flat 

 articular surface a foramen one sixth the diameter of such surface. It is the base of a 

 small conical cavity, the apex of which meets that of the cone of the opposite side, — a 

 beaded remnant of the notochord appearing to have traversed the vertebral column. In 

 other species examined by me certain cervical vertebras and a few consecutive dorsal 

 vertebras are ' opisthoccelian,' i. e. have the 4 ball ' in front ; and the convexity, in certain 

 of these, does not wholly subside until the lumbar region is reached. But whence did 

 Professor Huxley derive his knowledge of the ' opisthoccelous' character in ' pachypodal 

 Saurians' ? If from the original definition of the Dinosaurian group, 1 that character, as 

 there limited, seems to have stood the test of time. 



The discoverers of the Iyuanodon and Megalosaurus believed the ball to be behind, 

 and von Meyer accepted this view of the conformity of the Dinosaurian with the Croco- 

 dilian dorsal centrums. In fact, the way to distinguish the fore from the hind end of a 

 fossil saurian vertebra seems not to have been known to their describers until the test was 

 defined in 1841. This knowledge, howsoever acquired by the writer of the "Cha- 

 racter 1," here discussed, is applied by him in error to Dinosauria: in them the ball 

 subsides at the beginning of the dorsal series. 2 I would further remark, that, as there are 

 many modifications and characteristics of the so-called ' capitular transverse processes' and 

 ' tubercular transverse processes,' in the varied series, including Dinosaurian, of vertebral 



1 ' Report on Brit. Foss. Reptiles,' p. 91 : " Remarks on Mantell's « Fourth System' of Vertebrae from, 

 the "Wealden." 



2 lb., ib. 



