134 The Ottawa Naturalist. [Jan. 



being about four to six times their diameter distant from each 

 other. The polygonal ones have an average diameter of about 

 three-sixteenths of an inch, and, as in the trunk, a slight increase 

 in size is observed in those near the conical plates. Along the 

 side of the body the conical plates have their long diameter in a 

 fore and aft direction. 



The scale patterns above described are probably distinctive 

 of the species, and will no doubt, with the known ones of other 

 Cretaceous herbivorous dinosaurs, prove a reliable aid in specific 

 determination. 



The skin impression of a third Cretaceous herbivorous dino- 

 saur, shewn in plate XVII accompanying this paper, is part of 

 a large area of epidermal markings, from above the hip, preserved 

 with an almost complete skeleton of a trachodont obtained by 

 the vertebrate palaeontological expedition of 1912 from the 

 Edmonton formation on Red Deer river, and now exhibited as 

 a panel mount in the museum of the Geological Survey. This 

 specimen was thought to be referable to Trachodon marginatus 

 of the Belly River formation and was provisionally assigned to 

 that species. As the scale pattern of the integument of T. mar- 

 ginatus is now definitely known and proves to be quite different 

 from that of the Edmonton specimen it is clear that the latter is 

 not referable, to T. marginatus. It is now known with certainty 

 that T. marginatus had a footed-ischium but unfortunately in 

 the Edmonton specimen the distal ends of the ischia are not 

 preserved. 



The epidermal markings found with the Edmonton specimen 

 and already briefly described in a paper* by the writer, are 

 natural moulds and casts of non -imbricating scales of which some 

 are larger than others. The larger ones are flat or slightly con- 

 vex, polygonal in outline, and average about a quarter of an inch 

 in diameter; they are aggregated in irregularly oval clusters 

 from two to three inches in greater diameter, and about three- 

 quarters of an inch apart. Between the clusters are minute, 

 tubercle-like scales averaging about one-tenth of an inch in 

 diameter and forming the general ground- work of the pattern. 



This scale pattern is of the same general character as that of 

 < Trachodon annectens (Marsh), as described and figured by OsbornJ 

 in a specimen from upper Cretaceous beds in Converse count)-, 

 Wyoming, U.S.A., but is more pronounced; the oval clusters 

 of plate-like scales are larger, and the scales composing them 

 have a greater average diameter. The small sized tubercle-like 

 scales are much the same as in the Wvoming specimen. 



* Th a Naturalist, May, 1913, Th manus in a specimen of Trachodon Srom the 

 Edmonton formation oi Ubi rta. 



X Op. cit. 



