TRUE TEETH OF ORNITHORHYNCHUS. 229 
On a Specimen of the True Teeth of 
Ornithorhynchus. 
By 
Professor Charles Stewart, P.L.S. 
With Plate VIII. 
Tue interesting discovery by Mr. Poulton of the existence 
of true teeth beneath the epithelium of the jaw of a young 
Ornithorhynchus, of which an account was given by him in 
this Journal, vol. xxix, 1889, followed by a further descrip- 
tion given by Mr. Oldfield Thomas in the same year (‘ Proc. 
Roy. Soc.’), in which he pointed out that the teeth were not 
absorbed whilst still beneath the gum, but were functionally 
active until the animal had attained about half its adult size, 
made me anxious to obtain a specimen for the museum of the 
Royal College of Surgeons which would illustrate so remark- 
able and important an anatomical fact. A search amongst the 
rich stores of the College was fortunately rewarded by the 
discovery of a young male, 316 mm. in length, which showed 
these teeth in an extremely perfect state. . 
They were all provided with well-marked, slightly divergent 
fangs, mostly of a flattened form, which arose from some 
distance within the margin of the crown, to which their 
planes were parallel (the fangs had been absorbed in Mr. 
Thomas’s specimen). 
The upper jaws had two teeth on either side; they were 
very firmly attached by their fangs, and were surrounded by a 
thick epithelial ridge, which was continued beneath the crown 
