260 Mr. C. W. De Vis on Nototherium and Zygomaturus. 
apparent shortness of the tooth; but this again is also partially 
due to absorption of the posterior basal talon resulting from 
pressure in the rear. In short, the tooth before me is nothing 
but the somewhat mutilated, somewhat abbreviated, and some- 
what disguised homologue of its fellow. Most assuredly it is 
not the tooth of Notother‘um as known to me. Such is the 
ground, treacherous in itself and sadly misunderstood, which 
allowed my critic to sink into a veritable slough of surmise. 
To my question respecting the maxillary fossils which 
occur in frequency corresponding to that of the numerous 
mandibles of undoubtedly Nototherian origin, Mr. Lydekker 
responds somewhat inconsiderately to the effect that these 
“crushed Diprotodon-like skulls ” (all these terms are his own 
and unwarranted) may indicate ‘ young individuals or a small 
species of Diprotodon itself.” If this be so, nothing remains 
for me but to unlearn and relearn, if possible, the means of 
distinguishing between old and young Diprotodons, or, perhaps, 
in course of time to describe a “ small Diprotodon” with its 
posterior incisors on the edge of the jaw. 
This would not be a difficult feat for one prepared to say 
that Owenza is probably a “small form of Nototherium,” that 
is of Zygomaturus, since in Mr. Lydekker’s judgment a form 
with reduced dentition, small narrow nasals, elongated muzzle, 
and slender jugals may be one generically with a form anti- 
thetical to it in these and many other respects. Mr. Lydekker 
has very liberal ideas of the amount of differentiation some- 
times required for the establishment of a genus. 
With respect to the name Owenta, Mr. Lydekker remarks 
that it is preoccupied three deep in the Invertebrates, leaving 
it to be inferred that this also is a discovery of his own ; it is 
a distinct act of unfairness (unintentional [ should be willing 
to think) not to state that I called attention to the fact while 
pleading that under the circumstances the name might be 
accepted. 
Minor blemishes, such as terming my rejoinder to his foot- 
note in the B. M. Cat. of Foss. Mamm. a reopening of the 
question, I pass over, with merely a word on the “ untenable 
PEepORLTOHs which proposition briefly is that when a type 
acks a requisite characteristic that one of the proposer’s 
cotypes which does possess the characteristic required should 
for practical purposes be taken as the typical example. This 
seems to me to recommend itself to common sense. It may 
be observed that Mr. Lydekker himself holds the untenable 
by resting his case not on the molars of the type, but on the 
shape of the premolar deduced from that of the cotype. 
On the whole I have to thank Mr. Lydekker for his criti- 
