414 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
it as homologous with the part which I regard as the squamosal in 
that genus. But if I have correctly identified the squamosal in the 
Crocodilia, the element is in the right position for the quadratojugal, 
an interpretation which is supported by its covering the lower external 
surface of the quadrate adjacent to the articular surface. A compari¬ 
son of this bone in the Crocodilia (figs. Q and R) with the quadrato¬ 
jugal in Dimetrodon shows at once almost identical relations except 
that in the Crocodilia the quadratojugal has been produced upwards 
and forwards across the infratemporal fossa, actually joining the post¬ 
orbital by a special process. Gaupp (’94) reasoning from the rela¬ 
tionships of this bone (quadratojugal) in Gavialis, where it joins the 
postorbital directly below the squamosal, considered that this showed 
a primitive condition of the element (his paraquadrate) which lies 
above the quadratojugal in the lower forms and thus prevented him 
from considering it as the quadratojugal. To me, however, it is far 
more plausible so to consider it and to regard the process which joins 
it in Alligator and Gavialis to the postorbital as secondary in character 
and correlated with the extension inwards and forwards of the 
quadrate. 
The supratemporal has disappeared in the skull of the Crocodilia.. 
Fig. S. — Lateral aspect of the skull of Anchisaurus, after Marsh. J jugal; 
Mx., maxillary; Pmx., premaxillary; Po., postorbital; Qj., quadratojugal; 
Qu., quadrate; Sq., squamosal. 
Baur (’94), however, maintained that the squamosal was a complex 
of the ‘squamosal’ (supratemporal) and ‘prosquamosal’ (squamosal 
proper), but as in the case of his similar supposition with regard to 
Sphenodon, no embryological evidence has yet been advanced for the 
existence of the second bone. 
Dinosauria .— Two arcades are found in the temporal region of 
the Dinosaur skull (fig. S) and these are generally regarded as homol- 
