316 MR. W. K. PARKER ON THE OSTEOLOGY OF BALZNICEPS REX. 
Meckel’s cartilage. The external angular process is principally ossified from the 
‘ angular ’ element (but it derives its cartilaginous base from Meckel’s cartilage) ; the in- 
ternal angular process is ossified directly from the ‘ articular.’ All these processes may 
be seen equally well in the Pigeon or any common bird. Meckel’s cartilage lasts a long 
while in the Chelonia and Batrachia. In osseous Fishes it becomes large, and is often 
persistent. In the Chondropterygii there are no distinct osseous elements formed upon 
the simple mandibular cartilage. 
Tympanic Bone, 
Before entering upon the description of the spinal column of Balzniceps, it is neces- 
sary for us to say a word or two about the tympanic bone. 
The writer quite agrees with Késtlin, Goodsir, and Huxley, that the quadratum of 
birds is the homologue of the mammalian incus; if this is the case, where do we find 
the counterpart of the mammalian tympanic? Professor Huxley says’, very truly, 
“that the tympanic of the Mammal does not articulate with the lower jaw, nor with 
the pterygoid, nor with the jugal or quadrato-jugal.” Seventeen years ago we came 
upon a bony piece in the skull of a Pea-hen, which was carefully drawn at the time, 
and although examined and thought on again and again, it still continued to be an 
enigma,—the quadratum (as we were taught) standing for the homologue of the tym- 
panic. Renewed study, however, of the development of the skull in Birds and other 
Vertebrata, by various labourers, having restored the quadratum to its proper category, 
we are now at liberty to reconsider and to classify our nameless bone. 
This osseous piece of the skull of Pavo cristatus is of a spatulate shape, and is 
attached to that part of the auditory opening which is formed by the descending (par- 
occipital) ala of the occipital bone, just where it is confluent with the posterior angle 
of the squamosal. The narrow posterior end of the bone being thus articulated, the 
broad anterior part, which is somewhat notched and bifid, passes forwards and out- 
wards, protecting the membrana tympani, and partly serving to give origin to that 
membrane at its posterior superior margin. The length of the bone is three lines, and 
its greatest breadth two lines, so that it is sufficiently large to protect the membrana 
tympani for two-thirds of its extent at its upper margin. The attachment and rela- 
tions of this ossicle exactly agree with those of the tympanic bone of Mammalia, and its 
notched broad anterior margin appears to us to foreshadow the condition of the tym- 
panic in the Human foetus and in the adult Shrew and Echidna. We have searched in 
vain for this bony piece in any other bird, although the skulls of a great number have 
been examined. Hoping to find this bone again, at least in the Gallinz, we have made 
fruitless search for it in the skulls of the umdermentioned Gallinaceous genera; yet it 
may have been“ lost in those skulls that were prepared by maceration, and even in 
natural skeletons such a piece of bone would easily be dissected away, so that future 
* Croonian Lecture, p. 15. 
