55 



Sterkocephalus. Gen. uov. 



Stereocephalxjs tutus. Sp. noT. 



Plate XI, plate XII, figs. 1, 2, 3, 4 and 5, and plate XXI, figs. 6, 1 and 8. 



The specimen of which Adews from above, from the side and from below are given 

 on plates XI and XII, represents part of the plate-protected cranium of a herbivorous 

 dinosaur, that is, apparently, quite distinct from any hitherto described. 



With the head was fourd a transverse series of coossified sharply keeled scutes 

 which will be described farther on. 



The part of the head preserved is strongly convex transversely, but only moderate- 

 ly so from front to back. Coossified plates cover the whole of the upper surface and are 

 continued down on the vertical sides. They are arranged with a certain amount of 

 bilateral symmetry, are quite small at the centre and toward the back, but are larger in 

 front and very much more so on the sides. They are for the most part irregularly five or 

 six sided, with rather undulatorj^ surfaces that are marked by an irregular, raised, struc- 

 tural cross-hatching, feebly suggestive of the surface markings of the plates of Nodosau- 

 rus textilis, Marsh. Small vascular openings and grooves are also numerous on the 

 surface. The edges of the plates are as a rule angular and sometimes raised. Each plate 

 has its limit defined by a deep circumscribing furrow, so that although they are coossified 

 and form a continuous surface covering to the head, they do not lose their individuality. 

 A rounded node, or an incipient keel is noticed on some of the plates. 



The removal of sandstone from the lower surface of the specimen revealed the bones 

 of the palatal region (plate XII. fig. 2). The interpretation of these elements are as indi- 

 cated by the letters. The back ends, only, of the palatines (p.) are seen, meeting the 

 pterygoids in a suture indicated at " s." From here the latter bones (pt.) extend back- 

 ward on either side of interpterygoid vacuities (v.). The ridge (pb.) represents the 

 presphenoid and basisphenoid elements ; it is bent posteriorly to one side in the specimen, 

 which has been subjected to considerable pressure from above and is somewhat crushed 

 behind. 



From this interpretation of the bones of the palate it would appear that the part of 

 the armature preserved covers the upper part of the head near the union of the nasals 

 with the frontals. No indication of the orbits can be detected and it is probable that 

 they were placed far forward in the head. 



Part of a rib, having a T-shaped transverse section (Plate XII, fig. 5), such as is 

 characteristic of the heavily armoured Slegosauria, was found separately but in the same 

 locality, and is provisionally associated with S. tulus. The finding of such a rib is suffi- 

 cient evidence of itself to prove the existence, during the time of the deposition of the 

 Belly River series, of a large dinosaur having a heavy protective covering of bony 

 plates 



