MORPHOLOGY OF THE VERTEBRATE SKULL 31 
a new cartilage (analogous in newness to the ethmoturbinal 
cartilages), or a derivative of the hyoid. 
The reptilian extracolumella and suprastapedial (figs. 12, 20, 
22) have been homologized by many authors (including Peters, 
Cope, Baur, Dollo, Gadow 711, Broom ’07) with the mammalian 
incus and malleus. This is a ‘common sense’ theory, whose 
advocates regard the supposed transformation of the quadrate 
into the incus as an impossibility. The gist of their contention 
as presented by Gadow, is that the fenestra ovalis of the inner 
ear and the membrana tympani are fixed points, between which, 
Fig. 21 Schematic representation of Kingsley’s view of homologies in ossicula 
and jaw parts (A) of embryo lizard, (B) of embryo mammal (pig). According 
to this view the manubrium mallei has been derived from the extracolumella. 
c.t., chorda tympani. 
in the reptile, lies the columella-extracolumella chain and in the 
mammal the stapes, incus and malleus; that the ossicular chain 
of Sauropsida is consequently homologous as a whole with that 
of the mammal and that it is impossible to conceive the inter- 
calation into the mammalian chain of new elements, such as the 
quadrate and articular. But as shown above (p. 29), the quad- 
rate and articular, according to the best evidence available, were 
not ‘intercalated’ into the chain, they were functionally already 
a part of it. i 
In support of the hypothesis that the mammalian ossicula 
chain is homologous with the extracolumella + stapedial rod of 
