DR. G-UNTHER ON THE ANATOMY OF HATTERIA. 
597 
of advanced age, evidently consisted of two lateral halves in youth, and which diverges into 
two slight arched ridges in front, running across the posterior part of the postfrontals, 
and into two blade-like processes behind. Each of the latter joins a portion of the 
mastoid (h), forming the parieto-tympanic bars ; but, whilst in other Lizards ( Iguana , 
Varanus ) the parietal process forms the predominant portion of this bar, in Hatteria it 
is comparatively short, and far surpassed in extent by the mastoid portion. This bar is 
also much less backwardly directed than in other Lizards, being nearly at right angles 
with the parietal crest. The fontanelle in front of the sagittal suture, present in many 
but not in all Lizards, is also present here ; it is entirely within the parietals, although 
these bones are, at this place, overlapped by the frontals and postfrontals. 
The frontal bones are united by a distinct suture ; they are narrow, elongate, tapering 
in front and behind, forming but a small part of the orbit ; a very distinct groove runs 
along their lower edge for the reception of the olfactory nerve. Nasal bones large, tra- 
pezoid, forming the greater part of the upper surface of the snout, the nasal openings 
being entirely lateral and of rather inconsiderable width. 
The prefrontal ( i ) is narrow, with the outer margin nearly straight, not forming a pro- 
jection in front of the orbit; on the inner upperside of the orbit it extends backwards 
to its middle, but does not reach 'scvfar on the upper surface of the skull ; below it termi- 
nates as soon as it reaches the maxillary and palatine, covering the lacrymal (Jc) entirely, 
so that, of the latter bone, a small part only, above the ascending branch of the maxil- 
lary, is visible. 
We have now arrived at a portion of the skull which differs remarkably from that of 
other lizards, the homologies of which have been differently interpreted by authors, and 
which, therefore, deserves our particular attention — viz. the bones intercalated between 
the frontals and maxillary on one side, and the quadrate bone on the other. These bones 
form in Hatteria a vertical orbital bar which is connected by an upper (temporal) and 
lower (zygomatic) horizontal bar with the os quadratum. In all other Lizards (as far as 
they have been examined at present) the lower bar is absent, in some of them (Geckos) 
also the upper; and, again, in others ( Varanus ) even the orbital ring is incomplete, 
whilst in Crocodiles we find the same arrangement as in Hatteria. The bones composing 
these bars are the following : — 
1. The postfrontal ( l ) has a considerable extent, forming the hinder part of the roof 
of the orbit, and extending backwards to the commencement of the parietal crest ; there- 
fore it participates, at least externally, in the formation of the brain-capsule ; its poste- 
rior portion is crossed by an arched ridge. It is united by a suture with 
2. A three-branched bone (m), the upper branch of which contributes to the formation 
of the upper part of the orbit ; the second is directed backwards, forming one half of the 
temporal bar ; and, finally, the lower descends to the zygomatic, to complete the orbital 
ring. 
3. The temporal bar is completed by a portion of the mastoid (h), a branch of which 
descends along the anterior outer edge of the quadrate bone. 
4 m 2 
