44 THE ROYAL SOCIETY OF CANADA 



7. Irregularly shaped ossicles grading down to a very small 

 size. Extensive aggregations of these occur ventro-posteriorly on 

 the neck, and laterally on the throat, passing forward internal to the 

 mandibular rami to the symphysis. These ossicles are also numerously 

 distributed throughout the skin, filling the smallest interspaces be- 

 tween the larger scutes of definite shape. 



The above-mentioned scutes, most typical of special integumental 

 areas, grade more or less into each other, occasioning a great variety 

 of transitional forms. It may be noted that the change from the 

 flank scutes to the rectangular, ventro-lateral ones appears to be 

 abrupt. 



The larger-keeled scutes of the side of the neck and trunk are in 

 longitudinal rows, with the scutes lengthwise in each row. The rows 

 of scutes are near each other, and the scutes themselves in any par- 

 ticular row follow each other closely. So far as observed the rows are 

 fairly regular, and apparently those of any row do not alternate with 

 those of adjacent rows but have a transverse alignment. Smaller- 

 keeled, suboval scutes occur in the interspaces, and any intervals left 

 are filled by ossicles whose size and shape are governed by the extent 

 of the gaps remaining to be filled. 



The scutes occurring laterally on the neck and trunk have been 

 already referred to as being strongly-keeled. In these scutes the keel, 

 running lengthwise, in many cases somewhat obliquely and more or less 

 curved, is generally sharply angulated along the crest and usually in- 

 creases in height and basal breadth in its passage backward, ending 

 posteriorly in a more or less decided spur which oftien overhangs the 

 basal border of the scute. On either side of the keel the external surface 

 of the scute slopes to its upper and lower border either flatly or with a 

 varying amount of concavity, the latter depending largely on the extent 

 to which the keel is developed. It appears to be the rule that the 

 farther a scute is from the dorsal midline, the nearer the keel approaches 

 the lower border of the scute. Thus in scutes high up on the flank 

 the keel is nearly median, but in those forming the lower rows it rises 

 close to the lower border, apparently even overhanging it in the lower- 

 most row. These scutes are thickest posteriorly, and thinnest toward 

 the border in their anterior half. The internal surface is flat, or 

 slightly concave transversely, and posteriorly a rnarginal ridge is 

 frequently developed, giving this surface at this end the appearance 

 of being excavated. 



The surface of the scutes throughout is usually roughened by 

 irregularly disposed pits and depressions and externally, in addition, 

 by numerous vascular groove markings. The external surface has a 



