KLAIMERIDGIAN DINOSAURS. 567 



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, 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 shalt continued therefrom is less marked than in Cetiosaurun 

 longus (p. 585, fig. 4). 



The radial tuberosity (PL 70, figs. 1 and 2, j) is not developed distinctly as such, but, 

 as in Crocodilus and Varanus (il)., 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 Ptero- 

 dactyle 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, a) 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 ;/. The 

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

 ' pectoral ' h, 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, 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 cubiti' in Mammals. 



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

 terminates more abruptly than the ladial crest, at e, figs. 1 and 2, al)out seven inches 

 beyond the proximal end. The broad surface of the hiunerus 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.' 



The shaft at its narrowest part presents in section the form given in fig. 5, PL 70, 

 being almost flat, palmad and convex, anconad, transversely. It soon begins to expand 

 into the distal end of the bone. The crest, e, simulates the ' supinator ' one in 

 Mammals, and is not perforated, as is the answerable disto-radial crest in some 

 existing Saurians. Such perforation is very small in Varanus (ib., fig. 0, e). There 

 is no indication of this vascular or nervous canal in Omosaurus, and tiie crest is 

 i-elatively shorter than in Varanus. The ulnar expansion, f, of the distal end is thick 

 and tuberous. 



Sulficlent of the radial condyle, g, remains to sliow its Saurian extension palmad, and 

 its convexity in Omosaurus (ib., fig. 4) ; the precise form and extent of the less prominent 

 ulnar condyle or trochlea is not definable. 



The texture of the shaft of this humerus, as exi)osed by tlie fracture across its middle 



9^ 



