THYNG: SQUAMOSAL BONE. 
397 
Lateral to this supratemporal is a second element (Sq.) the supra- 
temporal of Huxley, Miall, Fritsch, and the others cited above, but it 
has also received other names. It is the ‘ausseres Paukenbein’ of 
Burmeister, squamosal of Baur (’86), Ammon, Boulenger, and Broili, 
the prosquamosal of Baur (’94), Williston, and others, and the para- 
quadrate of Gaupp. It articulates anteriorly with the postorbital 
(Po.) and the jugal (J .), medially with the supratemporal, and laterally 
with the quadratojugal (Qj.). Although we have little evidence of 
internal structures, its position is such that it must overlie the lateral 
portion of the otic capsule and the quadrate, the latter a structure in 
Trematosaurus, according to Burmeister (’49, p. 28-29) very similar 
to that of the Crocodilia. Since, then, this bone agrees in its position 
and in its relation to quadrate and otic capsule with the squamosal of 
the Urodeles and with the same element in the mammals in these 
respects, as well as in its articulation with the jugal, it follows that it 
must be called the squamosal and that the terms supratemporal and 
squamosal as usually applied to the Stegocephala and their allies must 
be transposed. The more lateral bone is the squamosal, the more 
medial the supratemporal which in recent Amphibia has disappeared 
entirely (or has possibly fused with the parietal) thus accounting for 
the large interval between the parietal and the squamosal in the em¬ 
bryos of both Amphibia and Mammalia. 
Now if this view be true that the supratemporal has disappeared in 
the Amphibia, Mammalia, and some other groups, we might expect 
that the supratemporal would show signs of reduction in some of the 
Stegocephala correlated with a corresponding increase of size in the 
squamosal. This is actually the case in many of the Stegocephala, 
as for instance the genera Pelosaurus, Melanerpeton, Archegosaurus, 
Chelidosaurus, Nyrania, Sclerocephalus, Loxomma, Rhinosaurus, 
Trematosaurus, Metopias, Capitosaurus, Mastodonsaurus, etc. Not 
only is there evident an increase of size of the squamosal but in some 
there occurs an overlapping of the supratemporal by the squamosal 
(vide Credner’s figure of Bra?ichiosaurus amblystomum, ’81-’89, vol. 
38, pi. 17, fig. 3). 
I claim no novelty in transposing the prevailing use of the terms 
supratemporal and squamosal in the Stegocephala. Similar usage 
may be found in the papers of Baur, Ammon, Boulenger, and Broili. 
Baur (’86) compared the Stegocephalian skull with that of the Lacertilia 
as described by Parker and Bettany but afterwards returned to the 
