MON OT HEM AT A 
31 
edge, and nre thus fitted for prehension : the other four teeth 
are of a somewhat irregular oblong oval form, about iMhs of 
an inch in length, and -^ths in width: the crown of theso 
teeth is concave, hut presents two transverse ridges; one near 
the middle of the tooth, and the other on the hinder part. 
These represent the grinder teeth, or true molars, of ordinary 
mammalia, and occupy the usual situation of such teeth; viz. 
immediately under the anterior root of the zygomatic arch. 
Besides these teeth, the Ornithorhynchus, in harmony with 
many other parts of its structure, presents a Reptilian cha¬ 
racter, in having horny teeth on its tongue; this is moderately 
long (terminating about half an inch from the end of the 
mouth), and has the upper surface of its anterior portion 
covered with minute papilla?; the hinder port is suddenly 
expanded, and at the same time is raised, and presents an 
acute angle in front, on which are observed a group of about 
six minute homy tubercles, and two others which are in the 
form of a depressed cone, and about-y^th of ,in inch in length- 
This bulb on the back part of the tongue would sene to pre¬ 
vent the passage of the materials collected in the mouth, toge¬ 
ther with the water, into the gullet, and to direct the former 
into those temporary receptacles, the cheek-pouches, which 
have their opening on each side, at the back part of the 
mouth 1 . The eyes are small, of a brown colour, directed 
somewhat upwards, and situated uear the base of the beak. 
The external orifice of the ear is placed at a short distance 
behind the eye, and being hidden by the fur, is not easily 
found in the dead animal, though readily seen in the living, 
which has the faculty of closing or opening it at will. The 
legs are strong, and very short; the feet are provided each 
1 In two specimens of Omithorhvnchus obtained by Mr. Bennett, be found 
the cheek-pouches tilled with mud and gravel; but in other cases their contents 
were found to consist of river insects, smaU shell-fish, etc.: these, however, 
were always mingled with mud or gravel. 
