Mr. R. Lydekker on Nototherium and Zygomaturus. 261 
cism; it has relieved me of a foolish fear that, in spite of 
improbability, the British Museum might possess some posi- 
tive evidence in natural association of parts that Zygomaturus 
is Notother‘um. Iam comforted to find that the hypothesis 
remains in its pristine purity, also to think that if no better 
attack upon my position can be made than that which I have 
met it is pretty secure. An utter failure to show that the 
right tooth is not the 2": proper to the skull, together with 
the confession that it is not the premolar of Nototherium, 
might well have released me from any obligation to cut Mr. 
Lydekker’s Gordian knot. 
Queensland Museum, 
April 15, 1889. 
XXXI.—WNote on the Above. By R. LYDEKKER. 
BEING extremely unwilling to enter into any prolonged con- 
troversy on this or any other subject, my remarks on the 
foregoing communication will be of the briefest nature. 
If the author be right in his contention that the first cheek- 
tooth on the right side of the cranium to which the name 
Zygomaturus was applied is homologous with and similar to 
the corresponding tooth on the left, then there may be evi- 
dence that this skull is specifically distinct from the form to 
which Sir R. Owen gave the name of Nototherium tnerme. 
This, however, would be very far from proving that these 
two forms are widely different and have a totally distinct 
type of appendicular skeleton. Moreover, if it be assumed 
that the so-called Zygomaturus is widely different from that 
type of cranium to which the author would restrict the term 
Nototherium, we are confronted with the difficulty that while, 
with one exception, all the complete maxilla in the British 
Museum appear referable to Nototherium, all the mandibles 
_ seem to be of the type of Zygomaturus. 
In conclusion, I cannot pass over the author’s extraordinary 
statement that the milk-teeth of Marsupials are always similar 
in structure to their successors, when, as is well known, pre- 
cisely the reverse is the case. ‘Thus we have only to cite the 
case of many of the Kangaroos, where a molariform “+4 is 
succeeded by a secant 2". This ignorance of such a well- 
known feature among existing forms is not calculated to raise 
one’s estimation of the author’s acumen when he has to face 
the more difficult question of the structure and affinities of 
extinct types. 
