I 
of the Ornithorhynchus paradoxus. y§ 
opening of the ear is at a great distance from the organ; and 
there is a cartilaginous canal, the size of a crow-quill, winding 
round the side of the head, upon the outside of the temporal 
muscle, leading to the orifice in the temporal bone. 
The memhrana tympani is larger than in other quadrupeds of 
the same size : it is of an oval form ; and the central part is drawn 
in, making its external surface concave. It has only two bones ; 
one passing directly from the membrane towards the foramen 
ovale, upon which there is a second bone, imperfectly resem- 
bling the stapes, having a flat surface of a circular form upon 
the orifice, and a small neck, by which it is united to the other 
bone. 
This structure of the bones is less perfect or complex than in 
other quadrupeds ; so that the organ altogether bears a greater 
resemblance to that of the bird. 
The organs of generation in this animal have several pecu- 
liarities of a very extraordinary nature. 
The male organs do not appear externally ; so that the dis- 
tinguishing mark of the sex is the spur on the hind leg. 
The testicles are situated in the cavity of the abdomen, imme- 
diately below the kidneys : they are large for the size of the 
animal. The epididymis is connected to the body of the testicle 
by a broad membrane, which admits of- its lying very loose. 
The penis in this animal does not, as in other quadrupeds, 
give passage to the urine. It is entirely appropriated to the pur- 
pose of conveying the semen ; and a distinct canal conducts the 
urine into the rectum, by an opening about an inch from the 
external orifice of the intestine. The gut, at this part, is de- 
fended from the acrimony of the urine, by the mucus secreted 
by two glands already described, which probably for this reason 
