152 Baron F. Nopcsa — On Stegosaurus prisons, sp, nor. 



Fig. 9d, very obliquely from the body, or else that the curve to which 

 it was attached must have had at least a diameter of 80 cm., if not 

 much more. 



As the lack of rugosities and the small size of the later caudal s 

 show that the end of the tail of St. prisms was not covered bv 

 powerful muscles and can scarcely have attained a diameter of 40 cm., 

 it is evident that these two particular spines of St. prisons cannot 

 have been situated on the tip of the tail, but must have been on some 

 other part of the body. Leaving the shape of the spines entirely out 

 of consideration, and judging only from the evidence afforded by the 

 other armoured European Dinosaurs, notably Scelidosaurus and also 

 Mylceosaurus and Polacanthus, one would never be induced to place 

 the dermal spines on the tail of our Stegosaurian, but on the scapular 

 region. This determination is apparently supported by the shape of 

 the actual surfaces of attachment of the bones in question. 



FlG. 9. a. Transverse section of dorsal dermal plate of St. prisons, with 

 indication of hypothetical attachment to body-tissue, b. Exterior view of 

 spine of the same animal, c. Interior view of the same piece, d. Marginal 

 view of the same piece, with indication of hypothetical body-tissue. 



Conclusion. — As already pointed out in the course of this paper, 

 St. prisons agrees in the stage of evolution of its dorsal vertebrae 

 somewhat with St. ungulatus, while in its limbs it holds an intermediate 

 position between 0. armatus and St. iingnlatus. In its pelvis it 

 corresponds with the genus Stegosaurus, though representing a new 

 species. 



Considering the development of the preacetabular part of the ilium 

 as a generic character, we may arrange the members of the genera 

 Stegosaurus and Omosaurus in the following manner: — 



Genus Omosaurus (Owen). Ilium not very elongate anteriorly, 

 widening backwards rapidly towards the acetabulum and the first 

 sacral vertebra, its anterior extremity rounded. Neural arch of dorsal 

 vertebrae slightly elevated. Five sacral ribs present. Sacrum much 

 depressed from top to bottom. 



