1896. ] MAMMALIAN DENTITION. 575 
cusp. The protocone is the largest cusp, while the para- and 
metacone form the outer border of the tooth and are separated 
by a slight notch only. 
In the feetus, in m. 1 the protocone forms the main mass of the 
tooth, while the para- and meta-cones form two rounded external 
shelves not at present conical; in m.2 the protocone and a small 
antero-external paracone are alone visible. The order of formation 
being :— 
1. Protocone. 
2. Paracone. 
3. Metacone. 
The lower molars are trituberculo-sectorial, the heel being larger 
than in Centetes but still very low; here also the protoconid is the 
first to develop, but it is quickly followed by the paraconid and 
later by the metaconid; the hypoconid appears as a low backward 
continuation of the dentine germ, 7. ¢. of the protocone, for it is a 
direct backward continuation of the base of that cone. The cusps 
develop in the following order :— 
1. Protoconid. 
2. Paraconid. 
3. Metaconid. 
4, Hypoconid. 
In describing the upper molars of Centetes and Ericulus, I have 
regarded them, as is usually done, from a tritubercular standpoint ; 
it is perhaps more correct to describe them a3 presenting a crown 
consisting of a large V-shaped internal cone sloping gently towards 
the external border of the tooth in the form of two ridges, which 
end in an external serrated margin consisting in Centetes of 4 
small cusps (Plate XX VI. fig. 34, a & 6, 1, 2,3, 4), two of which 
(2 & 3) are regarded as the paracone and metacone. Internal the 
main cone (5) dips sharply down to an internal cingulum, which 
is slightly expanded posteriorly (7). 
TALPA EUROPMA. 
It may seem unnecessary to reinvestigate the relationship of 
the milk and permanent teeth of the Mole, considering that all 
the details relating to these teeth appear to have been recorded by 
Spence Bate (1) as early as 1867, and that these have apparently 
been confirmed by Leche (9), who used the more modern method of 
serial sections; but unfortunately the former appears to have per- 
petrated one serious error, and the latter, owing to the fact that 
the specimens he examined where too young, has failed to rectify 
it. The point in question is the supposed presence of a needle- 
like deciduous first premolar in both jaws. 
Reference to Bate’s figures will show that he represents reduced 
but elongate needle-like predecessors to all the incisors, canines, 
and premolars, that preceding the 4th premolar alone being two- 
fanged and non-spicular in form. 
