606 Dr. A. Avnback-Cliristie-LinJe on the 



deep end of the tooth-band is thickened, forming a bud, as 

 in the upper V. 



Behind I^ the tooth-band swells out a little, to give rise to 

 a structure which may be a trace of the lower canine. This 

 structure being less distinctly differentiated than the corre- 

 sponding upper tooth-rudiment, I have only with some hesi- 

 tation designated it as a tooth-germ. In earlier stages this 

 rudiment may possibly be more differentiated fi'om the tooth- 

 band. 



In the foetal Neomys [Crossopus) fodiens the presence of 

 a lower canine is beyond doubt. 



Considering the above-mentioned facts, the next tooth is 

 most probably Pj, being here cup-shaped. 



Between this tooth and the last antemolar one, i. e. P^, 

 there are two rudimentary germs, those of Pv and P:^. P2 is 

 more distinctly differentiated from the tooth-band than P3. 



Woodward ^ has also observed the tooth-rudiment Po, but 

 regards it as the third lower incisor. 



P3 is represented only by a slight swelling of the tooth- 

 band. V^ is bell-shaped. 



As to the molars, M^ and M2 are represented, the former 

 by a bell-shaped, the latter by a cup-shaped tooth-germ. 

 M3 is not yet differentiated. 



Foetus : body -length about 13 mm. 



This stage does not differ much from the one just 

 described, only the rudimentary incisors are somewhat more 

 differentiated. 



The two halves of the tooth-band are connected in the 

 middle. The part of the tooth-band situated in front of tlic 

 large functional incisors presents three swellings ou each 

 side, which are still connected with the buccal epithelium. 

 These swellings most probably represent reduced incisors, 

 Ij, I2, I3. Transverse sections through these structures arc 

 here figured (text-figs. 4-6). 



In I4 tlie calcification has begun. The free deep end of 

 the tooth-baud is swollen. B(>tween l^aud l\ there is a gap, 

 but 1 could liiul no swelling of the tooth-band there. As to 

 the germs of the functional premolars, P.i is bell-shaped and 

 1\ is about to assume this form. 



* Woodward, M. F., " Coutributioiis to the Study of Mammalian 

 Dentition. — Tart II. On the Teeth of certain Insectivoia," Pioc. Zool. 

 Soc. Loudon, IbUti. 



