THYNG: SQUAMOSAL BONE. 
407 
The skull of Sphenodon (fig. M) has been studied by Gunther, Baur, 
Siebenrock, Osawa, Schauinsland, Howes and Swinnerton, and others. 
Fig. M. — Lateral view of the skull of Hatteria punctata, after Rabl. F., frontal; 
J., jugal; Mx., maxillary; N., nasal; Pa., parietal; PJ., postfrontal; 
Pmx., premaxillary; Po., postorbital; Prf., prefrontal; Qj., quadrato- 
jugal; Sq., squamosal. 
Both supra- and infratemporal fossae exist hence there are two bony 
arcades. The upper arcade separating the two fossae is composed of 
the postorbital (Po.) and 
an element (Sq.) which 
according to Howes and 
Swinnerton Ooi) and 
Schauinsland (:00) de¬ 
velops on the lateral sur¬ 
face of the otic capsule 
(fig. N) and later extends 
down upon the dorsal 
external surface of the 
quadrate (fig. O). From 
the fact that this bone 
shows intimate relations 
with both otic capsule and quadrate, that it connects anteriorly with 
the jugal ( J .) and the postorbital (Po.) to form the ventral and dor¬ 
sal arcades it cannot be regarded as other than the squamosal, its 
late association with the quadrate being the only deviation from 
what we have seen to be squamosal characteristics. The same rela¬ 
tions hold for the bone in Palaeohatteria and Stenometopon usually 
Fig 
N. — Lateral view of the developing skull of 
Sphenodon (Hatteria), after Howes and Swinnerton. 
Po., postorbital; Qu., quadrate; Sq., squamosal. 
