of the Ornithorhyncus paradoxus. 71 
one on each side of the upper and under jaw, and have broad 
flattened crowns. In the smaller specimens before examined, 
each of these large teeth appeared to be made up of two smaller 
ones, distinct from each other. The animal, therefore, most 
probably sheds its teeth as it increases in size. They differ from 
common teeth very materially, having neither enamel nor bone, 
but being composed of a horny substance only embedded in the 
gum, to which they are connected by an irregular surface, in 
the place of fangs. When cut through, which is readily done 
by a knife, the internal structure is fibrous, like nail ; the di- 
rection of the fibres is from the crown downwards. 
This structure is similar to that of the horny crust which 
lines the gizzard in birds. 
Between the cheek and the jaw, on each side of the mouth, 
there is a pouch, as in the monkey tribe, lined with a cuticle. 
When laid open, it is ij- inch long, and the same in breadth. 
In the female, it contained a concreted substance, the size of a 
very small nut, one in each pouch : this, when examined in 
the microscope, was made up of very small portions of broken 
crystals. 
Besides these grinding teeth, there are two small pointed 
horny teeth upon the projecting part of the posterior portion of 
the tongue, the points of which are directed forwards, seemingly 
to prevent the food from being pushed into the fauces during 
the process of mastication. This circumstance, of small teeth on 
the tongue, is, I believe, peculiar to this animal, not being met 
with in other quadrupeds. In the tongue of the flamingo there 
is a row of short teeth on each side, but in no other bird that I 
have seen. The teeth are represented in the annexed drawing. 
The forelegs are short, and the feet webbed; the length of 
