202 B. NATURAL HISTORY. 
square. Each half is united to the bone behind it, except at the 
median suture, by a double squamosal suture, the squamosal bone 
sending a plate below as well as above it. Medially the suture is 
single and serrate. Suspecting that the bone here determined to 
be parietal might possibly be frontal, I searched for a bone posterior 
to it, beneath the prolongation of the squamosal, but without suc- 
cess. That the squamosal should contribute to the brain-case is 
apparently anomalous among Reptiles, though not among warm- 
blooded Vertebrates; but if we suppose the anterior plate to be 
the epiotic the difficulty is much lessened. 
It might be objected that the position of the fontanelle was 
rather in favor of the determination of this bone as frontal, since it 
is, as in the Lacertilia, pierced in its posterior margin, and there- 
fore probably, as in that order, included between the frontal and 
parietal. But in reply it may be asserted that the position of the 
fontanelle in the two orders most nearly allied to the Ichthyop- 
terygia— i.e. the Anomodontia and Rhynchocephalia — justifies 
the interpretation I have placed on this bone. Thus, in the former, 
it is pierced in the middle of the parietal with a suture extending 
from it to the occipital suture. In the latter it lies near the poste- 
rior margin of the parietal, so far as visible; for the latter bone is 
doubtless overlaid by the squamosals, as in Ichthyosaurus. Giin- 
ther is probably correct in describing this median bone as parietal 
in Sphenodon. 
The long paired bones, immediately anterior, which extend to 
near the middle of the muzzle, are the frontals. They extend to 
the premaxillaries, a junction only found in Reptiles with posterior 
nostrils, as Pythonomorpha, Varanide, etc. but common among 
Fishes. In Sphenodon the frontals are unusually produced in 
front. 
Articulating with them on each side, and bounding the anterior 
and post and superior margins of the orbit, are the pre and post- 
frontals in their usual positions. The former almost excludes 
the latter from contact with the frontals, and leaves its connection 
with the parietal more extensive. Anterior to the frontals comes 
the elongate premaxillary. This of course bounds the nares in 
front; and as the latter are far removed posteriorly, in this order of 
Reptiles, the nasal bones have a posterior position also. The latter 
are much reduced in size, and have a very short suture with the 
frontals, being more extensively united with the lachrymal. They 
are entirely separated from each other by the anterior prolongation 
