IN THE OKNITHORYNCHUS PARADOXUS. 14s9 
The internal lamina of the small intestines is known to be 
very peculiar ; it forms a number of circular and parallel 
laminae close to each other, which diminish greatly the 
diameter of the canal. They are so incredibly numerous, 
as to give to the internal lamina of the intestines an extent, 
which I should scarcely think to be equalled comparatively 
in any other animal. These folds disappear near the ter- 
mination of the small intestines in the colon. The pecu- 
liarities in the termination of the rectunij in the structure 
of the cloaca, and anus, have been already noticed ; the 
most ample details relative to this part of the anatomy of 
the animal, and more particularly as regards the distribu- 
tion of the suspensor muscle of the cloaca, as being more 
connected with a systematic work, will be found in the third 
volume of the Anatomic ComparSe, 
There is little peculiar in the structure of the trachea 
and lungs ; the cartilaginous rings of the former are incom- 
plete, as in the Mammalia. The trachea divides at an 
acute angle into two bronchial tubes, which pass imme- 
diately to each lung : the whole inner surface of the wind- 
pipe is studded with small transparent cartilaginous bodies, 
like millet-seeds. A number of small glandular bodies were 
found close to the upper part of the trachea, and precisely 
in the situation of the thyroid gland, nor could any other 
be discovered. The elasticity of the lungs is considerable, 
and the capacity of the chest shewed that the quantity of 
jair taken in at each inspiration must be very great in pro- 
portion to the bulk of the animal. 
There is undoubtedly something of an ornithological 
character in the structure of the heart ; the \alves placed 
at the entrance of the venae cavae into the right auricle 
seemed to me in a great measure muscular ; and the right 
auriculo-ventricular valve was much more muscular than 
membranous. The bloodvessels had suffered so much by 
