Page 416 - My FlipBook

426 DENTAL ANATOMY.

cusp, thereby completing the second V. The last molar has a fifth cusp
behind, in this respect resembling many of the lemuroids.
The family most nearly approximated to this genus is that including
the shrews (Sorickke), Avhich always have two incisors both above and
below, greatly enlarged. In Blarina talpouJi'S, a living species of this
country, the teeth (Figs. 208, 209) are thirty-two in number, of which
Fig. 208.

Fig. 209.

Vertical View of Grinding
Side View of a Portion of a Skull of Blnrina ialpoides (much enlarged). Surface of o, a lower mo-
The si.xth tooth of the upper series is placed somewhat interDal to lar, and b. an upper mo-
the others, and is not repiesented in the drawing. lar (eularged)
twenty belong to the upper and twelve to the lower jaw. Owing to the
very early co-ossification of the premaxillae with the maxillse and the
paucity of suitable material, I am at present unable to give the proper
dental formula of this animal. Neither can I find any statement upon
the subject further than that of Owen, in M'hich he refers to the European
species, Sorex arcouvns, with only eight teeth u])on each side in the ujiper
jaw, and says:^ " The determination of the small teeth between the large
anterior incisors and the niulticus]>id molars dejiends upon the extent of
the early ankylosed intermaxillaries ; the incisors being defined by their
implantation in these bones, the succeeding small and simple crowned
molars must be regarded as premolars, not any of them having the
development or office of a canine tooth : their analogues in the lower
jaw are implanted by two roots." If he confines his statement to this
species, it is probably correct to refer all those teeth between the large
incisors and the anterior one of the last three to the premolar .series ; but
in Blarina there are six teeth to be disposed of. Allowing the normal
number of premolars (four), we have either three incisors and no canine,
or, as is most pro])able, two incisors and a canine, which would give the
following formula : I. ^, C 1, Pni. |-, M. |. This determination of
course may prove to be incorrect.
^ Odontofjyfiphi.; p. 41S.