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Hatteria punetata, its Dentitions and its Incubation Period. 
| By H. Spencer Harrison. 
With 6 Figures. 
In a recent paper (1) I have given an account of the develop- 
ment and succession of teeth in Hatteria. My results have led me to 
certain conclusions with regard to the past history of this remarkable 
reptile, and the main object of the present paper is to discuss the 
view I have put forward that the incubation period of Hatteria, at 
present an abnormally long one, has been greatly lengthened, and this 
so recently that the evidences of its former duration are still numerous. 
It will be necessary to briefly recapitulate some of my results, but 
for the details I refer to my former paper. 
The First, or Embryonic Dentition. 
This consists of a complete set of minute teeth, numbering about 
- on each side. They attain their maximum of development during 
the fourth month of incubation, i. e, some nine months before 
the animal is hatched. They do not fuse with the bone, and are 
never functional, being shed about the time of hatching. They no 
doubt represent a simple reptilian dentition of sub-conical teeth, which 
have undergone degenerative changes. 
The Second and Third Dentitions (the “alternating series”). 
The teeth which are functional in the newly-hatched animal form 
an alternating series, as is shown in Fig.1. From their development 
they almost certainly represent two distinct dentitions, the smaller 
teeth belonging to the second dentition and the larger to the third. 
Soon after hatching there are = of these teeth on each side (Fig. 2a). 
After this stage there is a very short cessation of tooth for- 
mation in the lower jaw succeeded by a renewed production from 
behind, the new teeth being uniform in size (uniform series, 
Fig. 2b). In the upper jaw on the other hand the alternating 
series receives additions in the same way until the animal acquires a 
length of about 20 cm, when a prolonged halt occurs. The total 
Anat, Anz. XX. Aufsätze. 10 
