On Cephalaspis magnifica from the Caithness Flagstones. 271 
comparatively gigantic C. Salweyi, Kgert., and C. Jexr, Traq. 
Being crushed perfectly flat, the contour of the shield appears 
broader than it would have been had its natural vaulting 
been preserved. The left cornu is perfect, but the right one 
is injured,—had that not been the case, the shield would 
have measured no less than 12 inches across in the flattened 
condition. The limits of the posterior margin of the shield 
are not very definite, and behind it there are some rather 
obscure remains of the body scales. 
The following measurements of the cephalic shield may be 
noted :— 
Length of shield from back to front, ; : - 83 inches. 
Semi-diameter from mesial line across broadest part on 
left side, . 6 a: 
Semi-diameter to tip of left cornu, : Bee ss 
From tip of snout to opposite anterior margins 153 ae : ea 
From tip of snout straight to tip of left cornu, 11 Sc 
Breadth across base of cornu, . LS: Nees, 
Length of cornu, 2F 
The snout is bluntly pointed, the cornu comparatively 
short and broad-based, as seen by the above measurements, 
and is not provided with any denticulations along the inner 
margin, 
The orbits are oval, 1 inch in diameter antero-posteriorly, 
8 inch transversely, while the width of the interorbital space 
is 1,2, inch. Owing to the extreme flattening of the shield, 
no traces are seen of the various fosse and prominences 
ordinarily seen in connection with the orbital region in _ 
Cephalaspis, except in the case of the “ post-orbital valley,” 
the position of which seems fairly well indicated. 
The contour of the reflected edge of the shield, which is, of 
course, ventral in position, is clearly seen through the dorsal 
portion, much of which has indeed been removed (and lost) 
with the counterpart of the fossil. This inferior rim is con- 
tinuous all round, and not open or interrupted behind as in 
Lankester’s figure of the lower surface of the shield in 
C. Lyell. It encloses a rounded-quadrangular area, whose 
angles are anterior, posterior, right, and left, and whose 
1 Fishes of the Old Red Sandstone, Cephalaspide—Paleont. Soc. for 
1869, p. 37, fig. 12. 
