No. 2.] HYOIDS AND OTICS OF BATRACHIA. 303 
tal half of the third ventral arch of the skull, and that the supe- 
rior half of the same becomes fused later with the second arch, 
thus forming the quadrate cartilage as it exists in adult Salientia. 
On approaching maturity, the ceratohyal leaves this connection, 
and is attached to the base of the skull as above described. My 
observations coincide with those of Parker in that the ossicula 
auditus do not appear until a later period of larval life in the 
genus Rana. But they appear before the ceratohyal has aban- 
doned its articulation with the quadrate cartilage. They then 
arise as follows: the epistapedial occupies from the first its 
normal position as a disk of cartilage at the flexure of the quad- 
rate cartilage. The interstapedial, on the other hand, arises as 
a bud from the normal position of its base, and gradually extends 
itself anteriorly. It early appears as cartilage with a short, free 
membranous extremity. The latter becomes the mesostapedial 
cartilage. These elements gradually elongate until they reach 
the epistapedial. For a time they reach no farther than the 
quadrate cartilage, and they rest on it, as in the Proteida and 
larvee of Urodela. 
CONCLUSIONS. 
From what has preceded, the following conclusions may be 
derived :— 
First. The relations of the stapes to the quadrate cartilage or 
bone are of two types in the Urodela. The one is possessed by 
the Proteida, Trematodera, Amphuimoidea, and Pseudophidia ; 
the other by the Pseudosauria and Trachystomata. The larval 
structure in the Pseudosauria, and inferentially in the Trachy- 
stomata, is identical with the structure characterizing the adults 
of the other division. This is confirmatory of the opinion which 
I have expressed 1 as to the origin of the genus Siren. This is to 
the effect that Siren is an animal which is descended from a 
land salamander, and that its immediate ancestor became 
aquatic again at a comparatively late period of geological time. 
My opinion was at first suggested by the condition of the bran- 
chize in very young animals, where they are functionally abor- 
tive, and do not become respiratory organs until later in life, the 
largest animals having the best developed gills. The characters 
1 American Naturalist, 1885, p. 1226. 
