598 
DR. GiTNTHER ON THE ANATOMY OF HATTERIA. 
4. The zygomatic ( n ) is much developed ; it emits one process to meet the lower branch 
of bone m, and a second to the os quadratum (o), forming the lower horizontal bar. 
As regards the second of the bones described (m), it is evidently the same which we 
find more or less separate from the postfrontal, and forming part of the temporal bar, in 
Lizards generally. It is described by Stannius (Vergl. Anat. Wirbelth. vol. ii. p. 159) as 
os qiiadrato-jugale ; but from the way in which he speaks of this bone as being found, 
“in most Saurians and the Crocodiles, connected with the os zygomaticum and frontale 
posterius,” and as “ constantly reaching the tympanic,” it is evident that he confounded* 
the temporal bar of the Lizards with the zygomatic bar of Crocodilians, and the bone in 
question with the squamosal of Crocodilians (see Cuvier, Oss. Foss. vol. v. pi. 3. fig. 1 ,p, 
or Owen, Anat. Vertebr. vol. i. p. 145, fig. 95, bone marked 27). The squamosal, as it 
exists in Crocodilians, belongs to the lower, zygomatic bar, and completes the connexion 
between the zygomatic and quadrate bones ; this squamosal is absent in Lizards generally, 
and also in Hatteria , where the zygomatic is in immediate connexion with the quadrate. 
On the other hand, the bone, more or less closely attached to the postfrontal in Lizards, 
does not exist in the Crocodile as an independent bone, the postfrontal entering into 
direct sutural connexion with the mastoid (temporal bar) and with the zygomatic : but 
from the position and form of the Crocodile’s postfrontal it is perfectly clear that this 
bone of Lacertians is nothing but a detached portion of the postfrontal ; and for such it 
has been taken by Cuvier, at least in Iguana (Oss. Foss. vol. v. pi. 16. fig. 23, i ) ; in 
Monitor and Varanus it is also present, although its sutural connexion with the post- 
frontal has been left unnoticed by Cuvier ; in Grammatophora it is absent. Professor 
Owen does not describe it as a separate bone (Osteol. Catal. vol. i. p. 663, or Anat. 
Vertebr. vol. i. p. 154), but mentions it as a continuous portion of the postfrontalf. 
Hollard, who has made researches into the developments and homologies of these 
bones, has come to the conclusion that the bone considered by Cuvier to be the mastoid 
in Reptiles and Fishes, is in fact the squamosal. A comparison of the skull of the Cro- 
codile with that of Hatteria seems to support this view, inasmuch as Cuvier’s “partie 
ecailleuse du temporal ” of Crocodiles appears merely as a segment of the zygomatic J, 
with which it is reunited in Hatteria. 
Very remarkable is the form of the os quadratum (o) and its junction with the hind 
part of the pterygoid (r) ; both bones are much dilated, forming a vertical plate composed 
of two laminae, the laminae being immoveably united by suture, the quadrate being the 
anterior plate, the pterygoid the posterior. This sutural kind of union appears to be 
unique among Lizards, which have those two bones united by a joint allowing of move- 
ability to a more or less considerable extent. The condyle of the quadrate has a deep 
* This view is maintained also in the 2nd edition, pp. 52 and 57. 
t It must he mentioned that Rathke (TJntersuchnngen iiber die Entwickelung der Crocodile, 1866, p. 33) 
does not appear to have observed a division of the postfrontal into two parts in embryos of an Alligator. 
X Rathke ( loe . cit. p. 34) has found it and the zygomatic in an equally advanced state of ossification whilst 
the tympanic was still nearly entirely cartilaginous. 
