1917] The Ottawa Naturalist. 73 



In the dentary there are forty-eight or forty-nine vertical series of 

 teeth with four or five and sometimes the stump of a sixth in each series. 

 The individual teeth are largest at the midlength of the magazine 

 and decrease in size toward either end of it, the posterior ones being 

 considerably shorter but only slightly narrower than those in front. 

 The inner enamelled tooth-surfaces, in lateral aspect, are nearly 

 lozenge-shaped in outline, with the longer diameter vertical, and fit 

 closely together quincuncially in a mosaic which is almost half covered 

 from below by the thin alveolar wall. There are about 230 teeth in 

 each dentary, this being many less than the number (406) ascribed to 

 Diclonius mirabilis by Cope in his description of that species in 1883. 



MEASUREMENTS OF THE SKULL OF EDMONTOSAURUS. 



Mm. 



Length of type skull measured in a straight line from the 

 posterior edge of the opisthotic to the middle of the anterior 

 premaxillary border 1114 



Horizontal length of same from anterior premaxillary border 

 to a point vertically below the edge of the opisthotic 

 (paroccipital) 1066 



Length of quadrate 420 



Breadth of skull (paratype) between the external convexity of 



the postfrontals behind the orbit. (The size of the skull in 



the type and paratype is about the same) 428 



Length of mandibular ramus of paratype without predentary__ 908 

 Length of dentary of paratype 780 



EXPLANATION OF PLATES. 



Plate II Left lateral aspect of the type skull of Edmontosaurus 

 regalis, one-seventh natural size. 



Plate III Superior aspect of skull of Edmontosaurus regalis, one- 

 seventh natural size. This view is taken from above with 

 the skull in the position in which it is shown in plate II, 

 viz., with the line of the teeth practically horizontal. 



Abbreviations: Ar, articular; D, dentary; Ex. oc, exoccipital; 

 /'. frontal; /, jugal; L J lachrymal; l.t.f., lateral temporal fenestra; 

 Mx, maxillary; N, nasal; no, nasal opening; O, orbit; Opo, opisthotic; 

 Orsp, orbitosphenoid (alisphenoid) ; P, parietal; Pof, postfrontal; 

 Pal, palatine; Pmx, premaxillary; Prd, predentary; Prf, prefrontal; 

 Prot, prootic; Pt, pterygoid; Q, quadrate; Qj quadrato-jugal; Sang, 

 surangular; Soc, supraoccipital; Sp, splenial; Sq, squamosal: s.t.f., 

 supratempotal fenestra; V, vomer. 



