26 PROCEEDINGS OP THE NATIONAL MUSEUM vor.. 77 



as the right half of the first transverse ring. The largest plate, a 

 composite of two paired scutes, is identified as the median part of the 

 second ring (fig. 1, pi. 5) ; the third plate consisting of two scutes is 

 provisionally regarded as completing the right half of the second 

 ring (fig. 2, pi. 5). 



The articulated Palaeoscincus skeleton illustrated by Matthew -^ 

 (pi. 8, fig. 1) shows the rings over the neck to consist of six scutes 

 each, the narrowest ring lying in front, and it is largely on the evi- 

 dence of this specimen that the provisional identification of these 

 elements is made. 



The upper surfaces of these plates are roughened by irregular, 

 shallow vascular pits and grooves that are so distinctive of all der- 

 mal elements. The under surfaces are fairly smooth and show no 

 traces of the coalescence of the individual scutes further than a slight 

 swelling of the bone following the course of the sutural union, but 

 on the dorsal surfaces their line of junction is marked by deep 

 -straight grooves. Each scute has a low longitudinal keel that origi- 

 nates on the front border, rising posteriorly where it terminates in 

 an obtusely pointed overhanging, spine-like projection. These keels 

 are asymmetrically placed. 



The first ring in its entirety evidently consists of six scutes divided 

 in this individual at the center into two plates. It appears very 

 probable, however, that other individuals might have the two halves 

 fused at the middle into one continuous ring of bone, although Stern- 

 berg found the same divided condition in the type of Edmontonia 

 longiceps.^^ The ring is broadly arched and has a length, measured 

 in a straight line across the arch, of 350 millimeters, a width on the 

 median line of 90 millimeters. The medial scute is rectangular in 

 outline with its greatest diameter transverse. Viewed from above, 

 however, this scute is pentagonal in shape due to the low lying pro- 

 jecting spine, which strongly overhangs the posterior border of the 

 scute. The keel on this scute is placed nearest the external side and 

 is slightly divergent from the median line as it runs backward. The 

 median scute has the keel nearest to the inner side, and the overhang- 

 ing spinous projection is more rounded and pointed than on the scute 

 previously described. The outer of the three scutes is subrhombic 

 in outline when viewed from above and the keel which originates on 

 the inner, anterior corner, pursues a diagonal course outward and 

 backward, the conical spine strongly overhanging its outer border. 



On the anterior border at the junction of the scutes there are 

 roughened indentations that suggest the points of attachment of 

 smaller dermal elements. Otherwise this border is beveled from 



^ Matthew, W. D., Natural History, vol. 22, 1922, pp. 334-335. 



21 Sternberg, C. M., Trans. Royal See. Canada, vol. 22, 1928, sec. 4, p. 104. 



