TECJE TEETH AND HORNY PLATES OP ORNITHORHYNCHUS. 11 
urged me to publish the fact in the f Proceedings ’ of the Royal 
Society, and greatly assisted me with more material. I 
received a cleaned skull of the same age, a cleaned left lower 
maxilla, and the partially cleaned posterior halves of right and 
left lower maxillae, and also found in the same bottle a piece 
of epithelium with the subjacent tissues attached, in which I 
rightly conjectured that teeth might be embedded. This had 
probably been removed from the cleaned left lower maxilla. 
The investigation of this material has afforded the means for 
this part of the present paper. 
A brief account of the structure and mode of occurrence of 
the teeth was read before the Royal Society, Feb. 9th, and has 
been printed in the ‘ Proceedings ’ (vol. 43, p. 353). 
I quote from this paper a passage which insufficiently 
expresses the extent to which I am indebted to Dr. Pax’ker. 
“ When it is remembered that Dr. Parker had put the sections 
aside for a time in consequence of the press of other work, 
intending soon to make use of them for the investigation of 
the skull, it will be seen at once that my association with this 
discovery is purely accidental, and that I have been treated in 
an extremely generous spirit.” 
Number of the Teeth. — There are certainly three con- 
siderably developed and large teeth in each upper maxilla. 
That this is the case is proved by the comparison of Dr. 
Parker’s consecutive sections, of which the most characteristic 
are figured in PI. 11, figs. 1 — 15 x 14‘5. It is also most 
probable that three teeth occur in each lower maxilla, but I 
can only be absolutely certain of the existence of two, corres- 
ponding to the posterior two of the upper jaw. These two 
lower teeth are figured iu PI. II, fig. 16 x 9, as they 
appeared in a dissected preparation of the posterior part of 
the right lower maxilla. Dr. Parker has kindly consented to 
add this preparation to the odontological series of the British 
Museum, where it will shortly be placed. The fragment of 
maxilla came to an end immediately in front of the anterior 
tooth, so that it was impossible to ascertain whether a tooth 
corresponding to the anterior upper tooth was present. The 
