ON THE REVATIONS OF FRE HYOID AND “OTIC 
EEE MENTS “OF “THEY SKEEETON: IN THE 
leva Mewe(Glalvaye 
EH D CORE, 
Tue characters of the hyoid bones of many Batrachia have 
been described by Dr. Parker? and Professor Wiedersheim,? 
and their otic elements have received much attention from the 
same authors. In both fields, however, much remained to be 
done. The otic elements of the Salientia have been extensively 
described by Parker, but no especial attention has been devoted 
to those of the Urodela by either author, except incidentally to 
other objects. In the present paper I desire to call attention to 
these elements in the Urodela, and to contribute thereby to the 
general theory of the morphology of the inferior arches of the 
skull. Whether light be thrown on the vexed question of 
the homologies of the suspensors of the inferior arches of the 
skull or not, it is desirable to see what this intermediate group 
of vertebrata contributes to its solution. I go over the types 
seriatim, commencing with the lowest. 
GANOCEPHALA. 
In the genus Trimerorhachis (Cope) there appears to be a 
distinct opisthotic bone in addition to the intercalare, as in 
the fishes. In form it is much like the prootic, but in reversed 
position ; its anterior thin edge forming a suture with the pos- 
terior thin edge of the latter. The two together form on their 
inferior surface a spout-like groove, which extends outwards, 
1 Read before the United States National Academy of Sciences, April, 1888. Ab- 
stract published in American Naturalist, 1888, p. 464. 
2 On the Structure and Development of the Skull of the Common Frog, Transactions 
of the Royal Society, London, 1870, p. 137; Ox the Structure and Development of 
the Skull in the Batrachia, \oc. cit., 1875, p. 601; On the Structure and Development 
of the Skull in the Urodelous Amphibia, loc. cit., 1876, p. 529. 
8 Das Kopfskelet der Urodelen ; Morphologisches Fahrbuch, 1877, pp. 352, 459. 
