CLASSIFICATION OF DEVONIAN FIsIIES 451 
of Pa. Ep. presents, near its inner extremity, a sort of socket, with 
which a peg developed from the plate S.s. is articulated. 
An irregularly triangular bone (y’) is connected with the anterior 
edge of Pa. Ep. and forms the posterior angle and part of the antero- 
lateral edge of the skull. It is succeeded by another irregular bone ‘x, 
which enters into the posterior and upper wall of the orbit, and unites 
internally with Fr., and anteriorly with a larger and still more irregular 
bone Pfr. The latter is connected internally with Fr., Eth. and Pmx. ; 
while externally it sends off, rather in front of the middle of its length, 
a short process, which passes directly downwards and divides the 
Fig. 20. Bones of the head of Clarzas. 
orbital cavity (Orb.) from the nasal cavity (Na.), Extending from the 
lower end of this process to the postero-lateral angle of the skull, 
bounding the orbit below, and fitting in by its convex margin, to a 
concave excavation of the bones 1+, 7, is a large spatulate bony plate, 
narrow in front, broad and expanded behind, and composed of two 
pieces, z and 2’. 
The cranio-facial shield thus composed is succeeded by an osseous 
girdle, which defended the anterior part of the body like the back and 
breast plates of a medieval warrior, and is divisible into two portions, 
the dorso-lateral and the ventral shields—the former composed of nine 
pieces, the latter of six. Of the nine pieces of the dorso-lateral shield, 
GG 2 
