106 THE CERATOPSIA 



When found, the animal lay fully articulated on its right side, but as this was the better pre- 

 served, its position was reversed in mounting so that now the right aspect of the completed mount 

 is exposed. 



In size, it is somewhat smaller, curiously enough, than are either of its Belly River predecessors, 

 Chasmosaurus or Monoclonlus (Centrosaurus), but exceeds both in relative robustness, especially of 

 the ribs. The lesser over-all length is due in part to the short tail. 



This skeleton is as yet undescribed but a few notes taken by the author may be of interest. 



The vertebral formula, except for the short tail, corresponds with that of the Belly River 

 genera. The eighth presacral bears the first long rib; the latter, and also the rib articulating with 

 the ninth vertebra, has a capitulum which bears upon the centrum of the vertebra as do the typical 

 cervical ribs. The sacrum, as restored, has low spines, equal in height, and separated from one 

 another by a slender line of matrix. Curiously enough, there are thirteen such spines. Whether 

 or not there are thirteen centra in the sacrum instead of the normal ten, one cannot at present tell. 

 The dorsal spines are also low although that of presacral XVIII is higher than the preceding one. 

 Not only are the caudals fewer than usual, numbering 38 as against 46 for Monoclonius (Centro- 

 saurus), and 45 for Chasmosaurus, but the distal vertebrae are small, which accounts, in part, for the 

 lesser over-all length. 



The first chevron is light and is borne on caudal IV. The last six or seven vertebrae are 

 without chevrons. The pubis articulates with the penultimate rib, and the last rib underlies the 

 anterior part of the ilium. These are points of agreement with Chasmosaurus. All of the dorsal 

 ribs seem heavy, due in part to the way the middle and after ones are swayed together as the speci- 

 men lies, so that they are in contact from rib number 12 to number 21. The posterior rib has a 

 decided curve backward, as it now lies. The ischia are curved as in Triceratofs, and meet in a short 

 symphysis. The scapula is heavy, the distal end widening out, and the median longitudinal ridge 

 not approaching so near the anterior border distally as it does in the Belly River genera. It shows 

 an evolutionary trend toward the condition seen in Triceratofs. The humerus is heavy, with a very 

 pronounced deltoid ridge. The position of the head of the humerus is such that the angulation of 

 the fore limb in life was similar to that of the earlier forms. There is no crest on the rear of the 

 proximal end of the humerus, as in Chasmosaurus, which makes one wonder whether the latter can 

 be correct (see p. 69). There is no mechanical difficulty in swaying the humerus backward as seems 

 to be true of the mounted Chasmosaurus skeletons. The ulna has a very robust olecranon which 

 heightens the feeling of mechanical power in comparison with Chasmosaurus. 



The pes, as preserved, shows no trace of the vestigial fifth digit seen in the Belly River forms. 

 This has apparently been lost from the specimen, as it is present in the mounted Triceratofs in the 

 American Museum. 63 



Genus ARRHINOCERATOPS Parks 

 Arrhinoceratops brachyops Parks 54 



PI. XII 



Holotype: No. 5135 Ct. R.O.M.; nearly complete skull without lower jaw. 

 Horizon: Edmonton formation. 



Locality: 3 miles above Bleriot Ferry, on the Red Deer River, Alberta. 

 Collector: University of Toronto Expedition of 1923. 



The generic and specific characters are described as follows: "Supraorbital horn cores large, 

 directed outwards and forward; nasal horn core absent; facial region short; crest relatively large, 

 subquadrate, flat; squamosals long; parietals with oval fontanelles of moderate size; anterior 

 process of jugal unusually long." 



r ' 3 Osborn, H. F., 1933, p. 12. 

 "Parks, W. A., 1925. 



