98 ON THE STAGONOLEPIS ROBERTSONI AND THE 
The angulated scutes may be roughly divided into three kinds: 
the broad, the thick, and the irregular. 
The broad angulated scutes (fig. 2) have a transversely elongated 
trapezoidal form,—one of the short sides, which it will appear is the 
outer, not being parallel to the other, but sloping obliquely outwards 
and forwards. The largest of these scutes which I have seen is a 
well-preserved specimen from Lossiemouth, which, with the exception 
of a very small portion of its anterior and inner edge, is entire. 
The anterior edge has a length of 4§ inches; the posterior of 42 
inches. The length of the scute in the middle line is 2! inches. 
The inner edge is straight; the outer, somewhat convex behind and 
concave in front, passes into the produced antero-external angle. 
The inner surface only of this scute was visible, but, by cutting away 
a portion of its substance, the ornamentation of the outer surface 
and its natural cast in the sandstone came into view, so that the 
relations of both surfaces could be observed. The contour of the 
outer surface is somewhat concave from before backwards, and 
the anterior edge of the scute is bevelled as in the flat scutes; the 
articular facet (a) thus formed is wider externally and internally than 
in the middle. 
About 12 inch from the inner edge, and therefore much nearer 
the inner than the outer, a strong longitudinal ridge appears upon 
the scute, and, rising posteriorly, ends upon the hinder edge of the 
bony plate in a sort of rudimentary spine (4), while anteriorly it 
gradually dies away. The outer face of the scute falls away rapidly 
on each side from the ridge, so that, while measured through the 
ridge, the posterior margin of the scute is 7 ths of an inch thick, ata 
distance of three-quarters of an inch from it, on the outer side, it 
measures hardly more than {th of an inch, and is but little thicker 
at a like distance on the inner side. 
The outer surface of this wzde angulated scute is sculptured in the 
same way as that of the flat scutes, but the pits are larger, and the 
marginal ones are so much elongated as almost to deserve the appel- 
lation of grooves. The posterior, most prominent part of the ridge, 
is devoid of sculpture. The inner surface of this and of other scutes 
of the same order is quite smooth, except posteriorly, where it pre- 
sents a fine transverse striation; and its contour is totally different 
from that of the outer surface. Transversely it is concave, each side 
sloping towards a longitudinal valley, which corresponds with the 
external ridge, and therefore lies altogether on the inner side of the 
! T have since seen a specimen of one of these scutes 54 inches wide by 24 inches 
long.—July 5th, 1859. 
