STRUCTURE AND AFFINITIES OF THE PLATYSOMIDA. 351 
oblique rows, whose direction is from above downwards and forwards; along its 
upper margin or ridge they are acutely V-shaped and imbricating (fig. 7). The 
free surface of all the scales is covered by a glittering layer of ganoine, orna- 
mented by scattered punctures passing into short grooves and streaks, the orna- 
ment usually fading away as we pass towards the hinder regions of the body. 
The shoulder-girdle also is constructed on the same type as in the Palecnis- 
cide. I have not obtained a satisfactory view of the plate, which in that family 
I have considered as post-temporal, but there is a well-marked supra-clavicular 
(s el, fig. 1) obliquely perforated above by the canal of the lateral line; its 
direction is more vertical than in the Paleoniscidee. This is followed by a strong 
clavicle (c/), of the same general form as in the last-named group of fishes, to 
the front of the inferior extremity of which there is articulated an in/ra- 
clavicular plate (7. cl), which is, however, proportionally shorter, while just 
behind the junction of the supra-clavicular with the clavicle we find a small 
post-clavicular of a narrow semilunar shape. 
The line of the top of the head, sloping pretty rapidly downwards and for. 
wards, shows a convexity over the region of the orbit, which has not the 
remarkably anterior position seen in the Paloniscidz, but is placed nearly 
right over the upper jaw; the snout, too, does not project in the same manner 
over the front of the mouth. Common as specimens of Hurynotus are in the 
Edinburgh district, I have never yet obtained a specimen giving a proper view 
of the bones of the cranial shield ; two short parvetals (pa) articulating with each 
other in the middle line, followed by two slightly larger /rontals (/), are all 
which can be made out with accuracy, owing to the crushed condition of the 
heads, though I have also seen indications of a squamosal and posterior 
frontal. The base of the skull is furnished with a powerful parasphenoid ; 
ossifications were doubtless present in its side walls, but cannot be described. 
The position of the suspensorium is nearly vertical, with perhaps a slight 
inclination forwards, consequently the gape does not assume quite the enormous 
extent characteristic of the Paleeoniscide. The mandible is stout; externally a 
dentary (d) and an angular element (ag) are visible, the former occupying nearly 
the whole extent of the jaw, and having its upper margin set with small obtuse 
teeth ; internally there is a splenial, also dentigerous. The maailla (ma, figs. 1, 
10, 11, 18, 14), always easily recognisable, is triangular, having two long sides, 
upper and lower, and a short posterior one, the latter being nearly vertical, with 
a slight backward inclination, while the upper margin slopes gently downwards 
and forwards to the bluntly pointed anterior extremity. The lower margin, 
nearly horizontal in position and very gently convex in contour, shows, seen 
from the outside (fig. 13), but few evidences of teeth, to get a proper view of 
which it must be looked at from within (figs. 10, 11, 14). Here it will be 
seen that a little in front of the posterior-inferior angle of the bone a narrow 
VOL. XXIX. PART I. 4x 
