408 



ROY L. MOODIE 



ence of these cells in small and ever diminishing numbers. In 

 explanation of the absence of these cells, or the lack of evidence 

 of their activity we find that only the more sluggish Mesozoic 

 reptiles exhibit solid limb bones. The more active theropodous 

 dinosaurs, the teleosaurs, the crocodiles, tm'tles and birds have 





Canalis |;-'vi'-\";, 

 ossificans /\ ■-- \- 

 perforATJS 



Foramen 



/ / \ \ \ A 



Fig. 6 A diagram based on actual material, showing in a medial section 

 the way in which the various growth characters are associated. The cones, 

 shown at the terminations of the 'Canales ossificantes perforantes' are shown 

 by photograph in plate 1, figures 2 and 4. 



