ERINACEUS 



119 



the blunt point of conical cusp somewhat in front of middle of 

 crown. Of these four unicuspid teeth the first is smallest, the 

 second and third sub-equal and larger, the fourth intermediate. 

 On posterior side of crown of each unicuspid there is a faintly 

 developed ridge extending to apex of cusp, this ridge tending to 

 rise posteriorly, especially in fourth unicuspid, to form a very 

 rudimentary secondary cusplet. First and second incisors invari- 

 ably single-rooted. Third incisor single-rooted, but root occasionally 

 showing trace of longitudinal furrow on outer side. Canine 

 usually single-rooted, the root with or without longitudinal 

 furrow ; but in a small series of specimens every stage may be 

 observed from this condition to a completely two-rooted tooth, 

 each root with a distinct alveolus. First premolar single-rooted, 

 the root often showing traces of longitudinal division, and perhaps 

 rarely double. Anterior lower incisor essen- 

 tially like the corresponding upper tooth 

 but not so high. Its shaft is directed 

 obliquely forward in line with symphysis, 

 the teeth of opposite sides parallel, separated 

 throughout by a narrow space. 

 Three succeeding teeth unicuspid, 

 the crowns similar in outline to 

 those of upper unicuspids, but an- 

 terior cusps obsolete and posterior 

 cusplets relatively better developed. 

 Second upper premolar scarcely 

 broader than the unicuspids, but 

 three-rooted and with a distinct 

 protocone, metacone and postero- 

 external commissure. Large upper 

 premolar with well developed pro- 

 tocone, hypocone, metacone and pos- 

 tero-external commissure, the cusps 

 much as in the molars except that 

 hypocone is relatively smaller and 

 metacone and its commissure larger 

 and more trenchant. Large lower premolar with a high anterior 

 three-cusped portion similar to first triangle of lower molars, 

 except that the metaconid is reduced to a slight thickening at 

 inner base of commissure of protoconid ; second triangle repre- 

 sented by a mere narrow ledge or thickened cingulum. First 

 upper molar sub-quadrate in outline, the crown slightly wider 

 posteriorly than anteriorly. Protocone with somewhat broader 

 base than the other cusps and with low ill-defined anterior 

 and posterior commissures. Paracone, metacone and hypocone 

 sub-equal, the metacone slightly larger than the others. All 

 three are subterete with faintly indicated commissures, that 

 extending outward and backward from metacone to rudimen- 

 tary metastyle the most distinct. Parastyle and mesostyle 



no. 23. 



Erinaceus europseus. Teeth. 



