28 
MONOTItEMATA. 
the ribs separated for a longer period than usual from the body of 
the vertebrae, and in the axis vertebra the ribs are not anchylosed 
even in the adult animal 1 . In this character, as well as in the 
great number of dorsal vertebrae, and consequently ribs, we per¬ 
ceive one of the many points of approximation iu the Ornithor- 
hynchus to the Oviparous classes. The transverse processes to the 
caudal vertebrce are very broad, flat, and much produced: the tail 
is broadest near the middle, where its width in the skeleton before 
me is one inch and two lines, but the w idth gradually decreases 
from this point to the apex, in consequence of the gradual short¬ 
ening of the transverse processes. 
The humerus is a short, broad, and strong boue, and has the 
internal condyle perforated. The ulna and radius are in contact, 
and the former is remarkable for having the olecranon very sud¬ 
denly expanded at the extremity. The hinder extremities are 
longer than the anterior, but the increased length is due almost 
entirely to the tibia and fibula, the femur being but little longer 
than the corresponding bone of the fore leg —the humerus. The 
fibula is remarkable for having the upper extremity continued con¬ 
siderably beyond the proximal end of the tibia, and with this free 
portion much expanded : a process is thrown out from the base of 
the expanded portion of the fibula to articulate with the tibia 
and femur. 
The Omithorhynchus inhabits New South Wales and 
A an Diemen s Land, and is called by the colonists the Water- 
mole— a name suggested by its aquatic habits, combined 
with some slight resemblance which it bears to the common 
European mole. Were we, however, to institute a comparison 
between the Oniithorhynclms and any animal from other 
parts of the world, it would be with the Mygale of the 
Pyiennees, or the allied species which inhabits Russia: here 
the resemblance, both as regards external appearance and 
habits, is very considerable. The native names of our animal, 
* I find the ribs of the axis vertebra unanchylosod in the skeleton in the 
British Museum collection, which is considerably larger than those in the 
College of Surgeons’ collection, where the same peculiarity has been noticed 
by Professor Owen. 
