220 THE AMERICAN NATURALIST.  [VOL. XXXIII. 
tilage of the lower jaw. A little later the quadrate extends to 
and fuses with the otic capsule a little above and in front 
of the fenestra ovalis. This we may term the urodele type of 
auditory ossicles, although it is a question as to how far they 
serve as a sound-transmitting apparatus, the tympanum being 
entirely absent in the urodeles. These features, then, are the 
possession of a quadrate which acts as a suspensor of Meckel’s 
cartilage, and at the same time articulates with the stapes. It 
may be noted, in passing, that in the Cæcilians the stapes is per- 
forated, much as in mammals, for the passage of the stapedial 
artery, a feature which adds to the probability that this ele- 
ment is homologous throughout the pentadactyle vertebrates.! 
Of the anura we have studied Pipa, and our results here are 
much like those of Gaupp upon Rana. In both of these gen- 
era the essential features from our present standpoint show no 
affinities with the urodeles, but resemble rather those of the 
sauropsida, and hence a description of the relations in a lizard 
will answer present purposes. 
In Sceleporus, which we take as the sauropsidan type, and 
in which we have studied several stages of the conducting ap- 
paratus, the auditory chain consists of a stapes lying in a fenes- 
tra ovalis, and, connected with this, a columella consisting of 
at first a cartilage rod extending horizontally outward into the 
tympanic membrane. When first differentiated, the shaft of 
this columella lies in the mesenchyma posterior to the entoder- 
mal diverticulum, the distal end of which expands later to form 
the tympanic cavity. In other words, tke columella is postspi- 
vacular. Another point of considerable importance, and one 
which has been neglected by most previous students of the audi- 
tory ossicles, is the relation of the stapedo-columellar tract to 
the adjacent nerves. The facial nerve, after leaving the cra- 
nium, passes backward just outside the otic capsule, running 
above the stapedo-columellar shaft. At the most posterior 
point of its excursion the facialis gives off a nerve, the chorda 
l In spite of this similarity between the auditory chains of Cæcilians and 
Amphiuma, we do not agree with Cope that the Cecilians have descended from 
Amphiuma, nor with the view of the Sarasins that Amphiuma is a neotenic gym- 
nophione. The senior author hopes to present his views upon these points at an 
early date. is 
