THYNG: SQUAMOSAL BONE. 
395 
lizard (c/. Gaupp, ’94, fig. 9) has relations to the parietal, otic capsule, 
and columella (=epipterygoid = ascending process of the quadrate) 
which are extremely similar to those described above for the bone in 
question in Ichthyophis. It should be recalled that Wiedersheim 
(’79, p. 21) suggested that possibly this bone might be “ein weit 
ausgewachsenes hinteres Stirnbein.” 
It will be remembered that the Sarasins have already recognized a 
postfrontal in the bone which nearly surrounds the orbit and which by 
various authors has been regarded as a postorbital, a sclerotic, or 
a supraorbital. In the light of its relations as described above, the 
‘jugal’ of the Sarasins corresponds more nearly to a postfrontal than 
does this osseous ring, which is therefore some other element. The 
Sarasins point out that the ring is not connected with the eyeball and 
hence cannot be a sclerotic, while its relations to postfrontal and frontal 
seem to negative its being a postorbital. Until further evidence is 
presented I am therefore inclined to call it a supra-orbital. 
From the foregoing it would appear that no squamosal is found 
in the Caecilians and therefore our determination of the squamosal 
must depend upon comparisons with the Urodele skull, the nearest 
of all living forms to the Stegocephala. 
Temporal Region in Stegocephala. 
In the Urodeles but a single bone occurs between the parietal and 
the quadrate, but in the Stegocephala (figs. B and C) two bones usually 
intervene. The homology of the parietals in the two groups cannot 
be doubted, but beyond this there is an element of uncertainty. Lat¬ 
eral to the parietal there is a bone ( St ., occasionally two as in Melan- 
erpeton and Discosaurus) bounded anteriorly by the postfrontal (P/.) 
and postorbital ( Po .), laterally by a bone ( Sq .) to be considered im¬ 
mediately, and posteriorly by the so called epiotic (Ep.) and supra- 
occipital (So.) plates. This bone is usually called the squamosal 
(Huxley, Miall, Fritsch, Credner, Fraas, Zittel, Baur, ’94, Gaupp, 
Woodward, Gadow, Williston, etc.) but it has received various other 
names—Schuppenschlafenbein (Burmeister), supramastoid (Cope), 
supratemporal (Baur, ’86, Ammon, Boulenger, and Broili). It over- 
lies the otic capsule and has no connection with either quadrate or 
jugal and hence cannot be termed the squamosal according to the 
