Zoology. 465 
families embrace the third type, in which the ceratohyal is articu- 
lated by suture with the quadrate. This last type is the most spe- 
cialized, since the larve of those families display the connection be- 
tween the ceratohyal and the skull similar to that seen in the ty 
second. Thus the Salamandride, which are superior to the Pletho- 
dontidz in their osseus carpus and tarsus and opisthoccelous verte- 
bre, have the hyoid connected with the skull as in the larve of the 
atter. 
Third.—At a stage in the history of the development of the Sa- 
lientia, the relations of the stapes and of the ceratohyal to the 
skull are the same asin a transitional stage of the Urodele family of 
Plethodontide. Or taken Separately, the relations of the stapes are 
those of Proteida, Trematodera, and larval Pseudosauria, while the 
relation of the ceratohyal is as in adult Plethodontide and Amblys- 
tomidæ. This is when the interstapedial cartilage connects the 
stapes with the posterior face of the quadrate cartilage, and when the 
ceratohyal articulates with the posterior face of the quadrate at its 
distal part. 
Fourth—lIt is not probable that the epistapedial forms an inte- 
gral part of a primitive element representing the ossicula auditus, as 
it originates independently of the interstapedial and mesostapedial. 
_ Fijth—The interstapedial and mesostapedial do not at any time 
ìn the history of the development of the genus Rana form any part 
of the ceratohyal or Meckelian ventral arches. As the incus and 
malleus of the mammalian ossicula auditus are segmented from the 
proximal parts of these arches, embryology indicates that they are 
not homologous with the ossicula of the Salientia. From this point 
of view the latter form a special line of development, distinct from 
that displayed by the Mammalia, unless the developmental reco 
as been greatly falsified by cenogeny. From the embryological 
standpoint it follows that the ossicula auditus of the Batrachia Sa- 
lientia must be excluded from the discussion of the homologies of 
the mammalian ossicula. 
Sizth.—But the characters of the Ganocephala and Rhachitomi 
permit the following reflections, since the latter order is the one 
from which the Salientia derived their descent. The existence of 
a well-developed columella auris which is unsegmented, in the for- 
mer orders, apparently like that of the Lacertilia, suggest that 
segmentation seen in the Salientia is a specialization of later origin. 
This columella has also the position of the proximal part of the 
ceratohyal in the adult frog and the larval salamander. As the 
position of this element in all but the youngest tadpoles is a result 
or Cenogeny, it may be inferred that the ossicula auditus of both 
the Rhachitomi and the Salientia represent the separated proximal 
= of that arch, and hence be truly homologous with the incus of 
ae mammal. The probability that this is the case is increased by 
p er of this element in the Pelycosaurian genus Clep- 
sydrops' where the columella extends to the cranial wall, leaving 
*See Proceed. Amer. Philosoph. Society, 1884, p. 41, Pl. 
