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no offshoots; if this is so, it is obvious that to arrive at sound con- 
clusions as to its affinities, we must, as far as possible, dis- 
tinguishfromtherest those characters which have arisen 
since the new conditions of development first affected 
the ontogeny. I have endeavoured to do this for the teeth, with 
the result that these are brought more into line with those of Palaeo- 
hatteria!), or perhaps Homoeosaurus. The downward projection of 
the premaxillary “teeth” is, I consider, quite valueless as an evidence 
of affinity. 
It is only possible to make suggestions as to the cause of the 
increased length of the incubation period. The fact that the animal 
was apparently once hatched at what is now the beginning of winter, 
and that little advance in development is at present made during this 
season, suggests that the climatic conditions were the cause of the 
change. There may have been a scarcity, or an increasing scarcity, 
of food, during the winter months, or even an alteration of climate. 
Denpy makes some statements that may perhaps be mentioned here. 
He says, “at Stage R a very remarkable feature makes its appear- 
ance, the nostrils being completely plugged up by a dense cellular 
mass derived from proliferation of their epiblastic lining’. In an 
Addendum he remarks on the coincidence that the embryo of Apteryx 
has a precisely similar plugging-up of the nostrils, as described by 
T. J. Parker. The phenomenon in Hatteria is I believe due to the 
lengthening of the incubation period. Ihave not succeeded in finding 
out how long Apteryx remains within the egg, but it seems quite 
possible that the occurrence of this plugging-up of the nostrils in two 
such unlike forms in one small province is something more than a 
coincidence. 
University College, Cardiff. 
List of Papers. 
1) Harrison, H. S., Development and Succession of Teeth in Hatteria 
punctata. Quart. Journ. Microsc, Sc., N. S. No. 174, 1901. 
2) Kixenruat, Zur Dentitionsfrage. Anat. Anz, Bd. 10, 1895. 
3) Röse, C., Ueber die Zahnentwickelung von Chamaeleon. Anat. Anz,, 
Wolk, 1893. 
4) Kükentuar, Die Waltiere. Jenaische Denkschriften, Bd. 3, Abt. 2, 
1893. 
1) Howss and Swinnerton (6) have discovered that during de- 
velopment the plastron of Hatteria passes through a Proterosaurian 
condition. 
