1896.] MAMMALIAN DBNIITIOir. 575 



cusp. The protocone is the largest cusp, while the para- and 

 inetacone form the outer border of the tooth and are separated 

 by a slight notch only. 



In the foetus, 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-externai paracone are alone visi ble. 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, i. e. 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 Oenteies and Ericulns, I have 

 regarded them, as is usually done, from a tritubercular standpoint ; 

 it is perhaps more correct to describe them a9 presenting a crown 

 consisting of a large V-shapcd internal cono sloping gently towards 

 tlie external border of tlie tooth in the foi'm of two ridges, which 

 end in an external serrated margin consisting in Centetes of 4 

 small cusps (Plate XXVI. fig. 34, a & b, i, 2, 3, 4), two of which 

 (2 & 3) are regarded as the paracone and metacone. Internal the 

 main cone (s) dips sharply down to an internal cingulum, which 

 is slightly expanded posteriorly (7). 



TaLPA EUEOPjEA. 



It may seem unnecessary to rdinvestigate the relationship of 

 the milk and permanent teeth of the Mole, considering that all 

 the details relating to these teeth appear to have \)een recorded bj' 

 Spence Bate (1) as early as 1867, and that these have apparently 

 been confirmed by Leciie (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. 



Eeference to Bate's figures will show that he represents reduced 

 but elongate needle-like predecessors to all the incisor^ canines, 

 and premolars, that preceding the 4th premolar alone being two- 

 fanged and non-spicular in form. 



