234 ROYAL SOCIETY OF CANADA 
SCUTES. 
The dermal armour is represented by over fifty pitted scutes none 
ef which can with certainty be said to have belonged to the ventral 
surface. The majority of the scutes are nearly square or oblong with 
rounded angles and a smooth, flat or transversely concave under surface. 
Those that are flat (or somewhat convex) beneath usually have the pits 
of the upper surface disposed without apparent order, those in which 
there is a decided transverse curvature to the plate (causing the under 
surface to be slightly concave) generally have a low, longitudinal keel 
developed above, from which the pits diverge on either side to a greater 
or less extent, with a tendency to show a radial pattern. In ‘ome 
specimens the keel extends the full leng.h of the plate, in others it is 
shorter or it may be reduced to a central raised area in which case the 
radiating arrangement of the pits becomes more pronounced. ‘Lhe 
scutes range in breadth from about 15 to over 50 mm. It is thought 
that those without keels may have belonged to the ventral surface. 
The pits are conspicuous, deep depressions separated from each 
other by a reticulation of smooth, narrow ridges. They vary in size 
considerably, their outlines being roughly circular, quadrilateral or 
polygonal with rounded angles, or oval with the major axis of the 
elongated ones in a direction as a rule at right angles to the inargin 
ef the scute. The supposed ventral scutes are ornamented with pits 
that show little variation in size and are nearly circular in outline. 
A dorsal scute is shown in plate V, fig. 15. It is broader than 
long, with a short longitudinal keel or central raised area from which 
the pits radiate. It is thickest (4.5 mm) at the centre and thins 
gradually in all directions outward; the front and hinder borders 
coming to a sharp edge. The sides retain a thickness vf nearly 2 mm., 
and are rough having probably been in contact with a scute on each side. 
The surface is smooth for a short distance back from the front edge 
forming a marginal tract that was overlapped by the scute immediately 
in front. The under surface is quite smooth and in a transverse 
direction slightly concave. 
Figures 16, 17 and 19 give representations of the scutes in which 
the keel extends almost their full length. These scu‘es have not a well 
defined smooth area indicative of having heen overlapped. ‘The edges 
in front and behind are thin but the lateral edges are rough particularly 
in the two smaller specimens (figs. 17 and 19) vh'ch exhibit su’ural 
surfaces of some thickness (about 4.5 in fig. 17). The under surface, 
in the three, is transversely concave. . 
A small almost circular scute (fig. 20) has a very decidedly co: cave 
