Lrg RAMSAY H. TRAQUAIR ON 
a tolerably acute angle, from which the inferior margin slopes first a little 
downwards and forwards, and then passes nearly straight forwards; the short 
posterior margin slopes gently upwards and forwards to the very obtuse and 
usually more or less truncated superior angle, from which the superior margin 
then slopes downwards and forwards 
to the anterior extremity, just before 
attaining which it sends off a small 
articular process directed obliquely 
upwards and forwards. The external 
surface is ornamented with minute 
pits and delicate reticulating ridges ; 
the inner surface shows a delicate 
ledge running longitudinally a little 
above the inferior margin and nearly 
parallel with it. The inferior margin 
of the maxilla is set with a single row 
Fic. 2.—Lateral View of the Head of Rhizodopsis sawroides. 
op. operculum ; s.op. suboperculum ; p.op. preoperculum ; : ; 
az.z. plates on the cheek; j. principal jugular; 1.7. of small teeth, cylindro-conical, acutely 
lateral jugular; m.j. median jugular; mz. maxilla; ’ : : 
d. dentary ; ag. angular; 7.d. infradentary ; or. orbit ; pointed, slightly incurved, and of 
s.o. suborbital; s.f. supratemporal; pa. parietal; sq. 
squamosal; p.f. posterior frontal; 7 frontal; p.ma. equal size. Their external surfaces 
premaxilla. 
are quite smooth and glistening under 
an ordinary lens ; they are usually placed pretty closely together, though some 
irregularity in their distances from each other is not unfrequently observed. 
Each of these teeth measures about ,j, inch from base to apex in a maxilla of 
11 inch in length. 
In several specimens are seen the sharp imprints of two small dentigerous 
bones (p.ma.) forming the front edge of the mouth below the snout, and placed 
between and articulating with the anterior extremities of the right and left 
maxilla, while they are joined with each other in the middle le. Each of 
these two bones is nearly as high as long; they are firmly fixed to each other, 
and also to the front of the cranial shield ; the posterior extremity of each fits 
into the angle between the anterior extremity of the maxilla and the little arti- 
cular process already mentioned in the description of the last-named bone ; the 
attached teeth, seen in impression and in section, resemble those of the maxilla. 
That we have here the true premazxille cannot for a moment be doubted ; it 
is therefore abundantly clear that this element in Rhizodopsis does not in the 
least resemble the bone interpreted as such by Messrs Hancock and ATTHEY, 
but that on the other hand it is quite conformable to the type of premaxilla 
found in other Crossopterygii, as indeed in the Ganoids generally. 
The mandible is longer than both premaxilla and maxilla put together, 
reaching, as it does, a little further back than the posterior extremity of the 
latter. Its depth is contained about four times in its length, its upper and 
