THE ORNITHORHYNCHUS PARADOXUS. 223 
Smaller Orni- | Larger Orni- 
thorhynchus. | thorhynchus. 
Breadth of the lower mandible at the base . “ ie 
Length of the tail from the vent 41 10 
Breadth of the tail at the root . Salt tabbed oer: 4 8 
Reeth, of fap fore foot pee: shieoniee yeniiant. + ee ees 3 5 
Breadth of the fore foot . 34 5 
Length of the hind foot . 4 8 
Breadth of the hind foot 3 5 
Distance between the eyes . . . - - - sss. 33 6 
Distance between the nostrils Pe eres ies lt 
From the exterior nostrils to the end of the mandible IRE a 
From the tip of the tongue to the end of the lower mandible + 4 
The circumstances which first attract attention in these singular objects are, the 
total absence of hair!, the soft flexible condition of the mandibles, and the shortness of 
these parts in proportion to their breadth as compared with those of the adult. 
The integument with which the mandibles are covered is thinner than that which 
covers the rest of the body, and smoother, presenting under the lens a minutely granu- 
lated surface when the cuticle is removed, which however is extremely thin, and has 
none of the horny character which the claws at this period present. The margins of the 
upper beak are rounded, smooth, thick, and fleshy : the whole of the under mandible is 
flexible, and bends down upon the neck when the mouth is attempted to be opened. 
The tongue, which in the adult is lodged far back in the mouth, advances in the young 
animal close to the end of the lower mandible ; all the increase of the jaws beyond the 
tip of the tongue, which in the adult gives rise to a form of the mouth so ill calculated 
for suction or application to a flattened surface, is peculiar to that period, and conse- 
quently forms no argument against the fitness of the animal to receive the mammary 
secretion at an earlier stage of existence. The breadth of the tongue in the larger of 
the young specimens was 3: lines ; in the adult it is only one line broader ; and this 
disproportionate development is plainly indicative of the importance of the organ to the 
young animal, both in receiving and swallowing its food. The mandibles are surrounded 
at their base by a thin fold of integument, which extends the angle of the mouth from 
the base of the lower jaw to equal the breadth of the base of the upper one, and must 
increase the facility for receiving the milk ejected from the mammary areola of the 
mother. The oblique lines which characterize the sides of the lower mandible in the 
adult, running from within outwards and forwards, were faintly visible on the corre- 
sponding parts of the same jaw of the young animal: a minute ridge at the inner sides 
of these lines indicates the situations of the anterior horny teeth of the adult. 
1 This is not accidental, as in many of the adult specimens sent over in spirit, for the cuticle is entire. In 
the specimens which Mr. G. Bennett discovered, the skin had a slight downy appearance. 
