OF THE ORNITHORYNCHUS PAUADOXUS. 163 
Of the ribs, which are seventeen in number, the first is 
attached to the sternum, apparently by cartilage ; the suc- 
ceeding four by bone, the cartilage being removed towards 
the centre of the rib ; the succeeding ten terminate in broad 
osseous plates, extensively moveable, though connected 
with each other. Of the two remaining to be described, 
one is attached by ligament to the preceding rib, but they 
do not terminate in bony plates, and may be considered as 
floating ribs. 
There is perhaps nothing more singular in the structure 
of the ornithorynchus, than the formation of the clavicle 
and scapula, which have altogether the appearance of the 
same bones in reptiles ; and, as seems to me, more particu- 
larly in the animal called Tupinambis* From a scarcity 
of specimens in my possession, I am by no means prepared 
to enter on the inquiry to which class precisely the bones 
composing this very complicated clavicle and scapula ought 
to be referred. We readily distinguish a clavicle composed 
of a broad flat portion, articulated with the anterior, that 
is, upper edge of the sternum, and a small horizontal branch, 
evidently incomplete in its mesial part, and intimately con- 
nected with a parallel branch of the flattened portion of the 
clavicle *. These latter branches are joined with that por- 
• The fossil animal described in the Philosophical Transactions for 1818, 
has a sternum and clavicle very analogous to the Ornithorynchus, This 
analogy, which has been very beautifully pointed out by Sir E. Home- and 
Mr Clift, is even more perfect than these gentlemen suppose ; for I per- 
ceive, by the accompanying drawing (Phil. TranSi 1818, Part I. Plate II.) 
that the two small bones just described by me, as being present in the Or- 
nithorynchus paradoxus, have escaped their observation. Hence the distin- 
guishing marks between the bones composing the sternum and shoulder in 
these two animals does not consist in the fossil animal having a clavicular 
bone, which is wanting in the Ornithorynchus paradoxus, but rather in this 
clavicular bone or fourchette being united throughout its whole length with 
the scapula in the one, and with the clavicle or upper bone of the sternum 
L 2 
