316 MR. W. K. PARKER ON THE OSTEOLOGY OF BAL.ENICEPS 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 Balseniceps, it is neces- 

 sary for us to say a word or two about the tympanic bone. 



The writer quite agrees with Kostlin, 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 

 i^>*c 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 sufiiciently 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 Gallinee, 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. 



