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FOSSIL REPTIL1A OF THE 



of such ' Plates ' will be appreciated, the requisite comparisons being much facilitated, 

 and accurate results ensured, by such life-size figures. 



§ 7. Humerus. — Of the skull, teetb, or scapular arch of Omosaurus I have not 

 as yet received evidence. The humerus and some other bones of the left fore limb 

 (PI. XVII) have been relieved from the matrix in a more or less complete state. 



The humerus (ib., figs. 1 — 5) is remarkable for its breadth, especially at the proximal 

 half, compared with the length. The articular surfaces at both ends have been more or less 

 abraded. That at the proximal end (figs. 1 and 2, a and fig. 3, a) shows the elongate oval 

 form, with the larger end, c , toward the ulnar aspect, narrowing to the beginning of the great 

 radial crest, b', b', as in Crocodilus^ (Pal. vol. for 1858, p. 15; 'Cretaceous Reptiles,' 

 Tab. HI, fig. 12), Varanus, and most existing Saurians ; as in these, also, the head projects 

 somewhat toward the anconal surface (as at a, fig. 2) ; but the prominent part of the 

 shaft continued therefrom is less marked than in Cetiosaurus longus (Pal. vol. for 1875, 

 'Mesozoic Reptilia,' p. 32, fig. 3). 



The radial tuberosity (PI. XVII, figs. 1 and 2, b) is not developed distinctly as such, 

 but, as in Crocodilus (Monogr. cit., Tab. Ill, fig. 11, b) and Varanus (PI. XVII. fig. 6, b), 

 is the beginning of a plate or crest of bone, answering apparently to both the deltoid 

 and pectoral in Mammals, which plate extends considerably radiad, but with less inflection 

 palmad, than in Crocodilus or Varanus, so that more of its breadth is seen in a direct 

 palmar view, as in fig. 1, than in the Pterodactyle or the above existing Reptiles. It has 

 a certain forward or palmar bend, and subsides a little below the middle of the shaft. 



From the proximal beginning, b, of this great crest, a broad tuberous rising (ib., 

 fig. 2, d) projects anconad, and is continued, narrowing obliquely distad, to terminate or 

 subside at the radial side of the shaft, close to the termination of the crest b'. The 

 tuberosity and ridge, d, a, might be regarded as ' deltoidean,' as distinct from the 

 ' pectoral ' b, b', save that its position is anconal instead of palmar. There is a rudiment 

 or indication of this ' anconal ridge ' in the humerus of the Crocodile (Monogr. cit., 

 vol. for 1858, Tab. Ill, fig. 10, d), and a shorter one in Varanus. In the latter existing 

 Saurian it gives origin to a muscle answering to the external ' head ' or portion of 

 the ' triceps extensor cubite" 1 in Mammals. 



The ulnar tuberosity extends ulnacl and distad as a thick tuberous ridge, which 

 terminates more abruptly than the radial crest, at c, figs. 1 and 2, about seven inches 

 beyond the proximal end. The broad surface of the humerus between the crests is rather 

 concave across on the palmar surface, somewhat more convex on the anconal surface, 

 which is interrupted by the ' anconal or tricipital tuberosity and ridge.' 



1 The terms of aspect and position are the same as those defined,'p. 13 of the above-cited Monograph. 

 Mr. Hulke uses the term 'ventral' to signify the 'anterior' or 'palmar' surface, and 'dorsal' to signify 

 the opposite, 'posterior,' or 'anconal' surface; but he also applies the term 'ulnar' as synonymous with 

 ' posterior' in his description of a humerus referred to the genus Hylceosaurus. — 'Quart. Journal GeoL 

 Soc.,' 1874. 



