120 MONOTREMATA 
something like that of a duck, bordered by a naked and‘very sensitive 
membranous expansion. The place of teeth in the adult is supplied 
functionally by horny structures, elongated, narrow, and sharp- 
edged, along the anterior part of the sides of the mouth, and broad, 
flat-topped or molariform behind. Functional molar teeth present 
in the young and adolescent condition. Legs short, fitted for 
swimming ; feet webbed, each with five well-developed toes armed 
with large claws, beyond which in the fore feet the interdigital 
membrane is extended. Vertebre: C 7, D 17, L 2,8 2, Ca 21. 
Acetabulum not perforated. Tongue not extensile. Mucous mem- 
brane of small intestine covered with delicate, close-set transverse 
folds or ridges. Tail rather short, broad, and depressed. Eyes 
very small. Fur close and soft. 
The Duck-billed Platypus (Platypus anatinus) was the name 
assigned to one of the most remarkable of known animals by 
Shaw, who had the good fortune to introduce it to the notice 
of the scientific world in the Naturalists Miscellany (vol. x., 1799). 
In the following year it was independently described by Blumenbach 
(Voigts Magazin, ii. p. 205) under the name of Ornithorhynchus 
paradoxus. Shaw’s generic name, although having priority to that 
of Blumenbach, could not be retained, as it had been used at 
a still earlier time (1793) by Herbst for a genus of Coleoptera. 
Ornithorhynchus is therefore now universally adopted as the scien- 
tific designation, although Duck-billed Platypus or Duck-bill may 
be conveniently retained as a vernacular appellation. By the 
colonists it is called “ Water-Mole,” but it need scarcely be said, 
its affinities with the true moles are of the slightest and most 
superficial description. Until the last few years the early stages 
of the development of the young were not fully known. It had, 
indeed, been repeatedly affirmed, in some cases by persons who 
have had actual opportunities of observation, that the Platypus lays 
eggs ; but these statements were generally received with scepticism 
and even denial. This much-vexed question was, however, settled 
by the researches of Mr. W. H. Caldwell in 1884, who found that 
these animals, although undoubtedly mammals throughout the 
greater part of their structure, are oviparous, laying eggs, which in 
the manner of their development bear a close resemblance to the 
development of those of the Reptilia. Two eggs are produced at 
a time, each measuring about three-fourths of an inch in its long, 
and half an inch in its short, axis, and enclosed in a strong, flexible, 
white shell. 
The Platypus is pretty generally distributed in situations 
suitable to its aquatic habits throughout the island of Tasmania 
and the southern and eastern portions of Australia. Slight variations 
in the colouring and size of different individuals have given rise to 
the idea that more than one species may exist; but all naturalists 
