AET. 16 FOSSIL REPTILES FROM MONTANA GILMORE 27 



below upwards, leaving a narrow rounded edge whose surface is 

 slightly roughened. The scutes vary from 26 to 36 millimeters in 

 thickness around their borders. From the rounded character of the 

 outer border of the third or lateral scute, it seems quite probable 

 that it represents the lateral termination of the first ring. 



The two coossified scutes, shown in Figure 1, Plate 5, are thought 

 to represent the median pair of the second dermal row Avhich in this 

 instance are fully coossified on the median line as in Panoplosaurus. 

 These scutes in transverse curvature, thickness, outline of posterior 

 border, and keel development show a close resemblance to the homol- 

 ogous elements of Panoplosaurus mirus. In proportion and outline 

 as a whole and in minor features they show many dissimilarities and 

 strongly suggest that differences found in the armor of Palaeoscincus 

 and PanoijlosauTus when fully known will greatly assist in dis- 

 tinguishing these genera. 



The median coossified plates of the second row measured in a 

 straight line across the ventral side have a greatest transverse width 

 of 390 millimeters ; on the median line a length antero-posteriorly of 

 130 millimeters. The keels of these scutes are placed nearest the 

 outer border, whereas in Panoplosaurus they are near the inner edge. 

 The posterior end of the keel develops a low, obtusely rounded spine 

 that overhangs this edge. 



The third plate consisting of the two coossified scutes shown in 

 Figure 2, Plate 5, is identified as completing the right half of the 

 second ring. That the smaller one represents a lateral scute seems 

 to be indicated by the rounded outer border and the strong diagonal 

 trend of the keel. 



Spined scutes. — Massive, long, sharply pointed spined scutes, such 

 as are found on the shoulders and along the sides of Palaeoscincus 

 (see pi. 8) are present, and are illustrated in Plate 6, Figures 1, 2, 

 3, and 4. 



A pair of moderately sized spinous scutes apparently corresponding 

 to those lateral to the ends of the second transverse ring (fig. 3, pi. 6) 

 in the Palaeoscincus skeleton are in perfect preservation. Their 

 bases are subovate in outline, measuring 205 millimeters in the 

 longest diameter and 133 millimeters in the shortest. These ends 

 are deeply concave and around the borders a rugose band indicates 

 clearly the depth of their insertion in the integumentary covering. 

 On the superior surface, a high, triangular-shaped spinous keel is 

 developed, overhanging the basal portion. Over all, this scute has 

 a greatest height of 290 millimeters. The surface of these bones 

 is covered by the usual shallow vascular pits and grooves. 



A single scute, the largest of the series, doubtless corresponds to 

 the second in this row of lateral spines, and occupies a position over 



