DevAopmenl of the Teeth of the Soviclila'. 009 



in the text only one labial bud, Avhicli be regards as LP (/. c. 

 pp. 28, 30). 



No doubt tlie last-mentioned bnd ouglit to be interpreted 

 in the same way as the corresponding one {PI.) in Sorea', 

 i. e. as a prelacteal vestige, the real third milk-tooth, Id^, 

 being an early vanishing structure. 



Fains : hody-lengtli ilhout 13 mm. 



In this foctns only those milk-teeth which in the last- 

 mentioned specimen are cup-sliapcd, i. e. Id*, Pd', Pd^, and 

 Pd', arc remaining. They are all represented by very 

 minnte calcified tooth-rndiments, which probably never cut 

 the gums. The presence of calcified milk-tectli in Sorex is 

 thus substantiated. 



Young Sorex : lody-leiujth about 33 mm. 



I have found no trace of upper milk-teeth in the young 

 Sore.v. As tlie specimen examined was blind and almost 

 hairless, and consequently at most a few days old, it is most 

 probable that the milk-teeth disappear before birth. 



The lower jaw. 

 Foetus: hody-lencjth about 11 mm. 



The first transverse sections through the tooth-band show 

 a labial growth of it at the point where it gives rise to the 

 structure designated by me as Ij. This growth I have 

 interpreted as a vestigial Idj. 



There are no traces of other milk-incisors. 



The following milk-tooth-germs are related to P^, V^, and 

 P4. Pdj is cup-shaped ; Pdg is a highly vestigial structure. 

 In Pd^ the calcification has begun. 



Foetus: body-length about 13 mm. 



Also at this stage a vestigial trace of Idj is distinguishable; 

 Pdj and Pd^ are calcified. 



Young Sorex : body-length about 33 mm. 



Pd^ is present, represented by a minute calcification which 

 Avill evidently soon be absorbed. 



Pd^ is thus the only milk-tooth surely present at birth, all 

 the other upper and lower ones most probably disappearing 

 before birth. 



