406 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
temporal but supra-and infratemporal fossae as well, while squamosal, 
supratemporal, and quadratojugal bones persist, thus indicating a 
position intermediate, so far as the temporal region is concerned, 
between Sauranodon on the one hand, and Palaeohatteria, Steno- 
metopon, and Sphenodon on the other, in which, while the three 
fossae occur, the supratemporal bone has disappeared. 
In Dimetrodon (fig. L) as reconstructed by Case (’98) the supra¬ 
temporal (squamosal of Case and of Williston) articulates laterally 
with the squamosal (prosquamosal of Case, quadratojugal of Williston) 
and, by joining the short posterior process of the parietal, forms the 
Fig. L. Posterior lateral view of the skull of Dimetrodon, after the recon¬ 
struction of Case. F frontal; J., jugal; Pa., parietal; Pf., postfrontal; 
Po., postorbital; Qj., quadratojugal; Qu., quadrate; Sq., squamosal; St., 
supratemporal. 
lateral border of the post-temporal and the postero-median border 
of the supratemporal fossa. Lateral to the supratemporal and over- 
lying the quadrate (Qu.) is the squamosal (Sq.) bounded on its ventro¬ 
lateral margin by the quadratojugal. It articulates, also, with the 
postorbital (Po.) forming with the later the arcade separating supra- 
and infratemporal fossae. The quadratojugal (prosquamosal of Wil¬ 
liston) is intercalated between jugal, squamosal, and quadrate. 
The relations in Palaeohatteria, Stenometopon, and Sphenodon 
are so nearly alike that they may be conveniently considered together. 
