304 ANATOMY OF VERTEBRATES. 



jaws. The first three, I, in the upper jaw are very small, with 

 simple incisive crowns, and are each implanted by a long and slender 

 fang in the premaxillary, 22 : these teeth are incisors. The next 

 tooth, c, by the size and shape of the crown, represents a canine, 

 but it is implanted by two fangs, like the succeeding premolar 

 teeth. Three of these teeth, p 1, 2, 3, are of small size, with 

 compressed conical crowns ; the fourth premolar, p 4, has a larger 

 three-sided conical crown, supported by three fangs : the crowns 

 of the true molars, m 1,2, 3, are multicuspid ; the middle one the 

 largest, with five points, and usually supported by four fangs, the 

 hindmost the smallest, with a tricuspid crown and three fangs. 

 In the lower jaw the first four teeth on each side are small, simple, 

 and single-fanged, like the three incisors above, but the outer- 

 most, c, is the largest ; the fifth tooth has a large laniariform 

 crown, supported by two fangs, being very similar to, but shorter 

 than, the two-fanged canine above. As it passes behind that 

 tooth when the mouth is shut, we must regard it as a premolar, 

 p \ : it is the first and largest of the series of four premolars, 

 each of which has a small posterior talon at the base of the com- 

 pressed conical crown. The three true molars, m 1, 2, 3, are 

 each implanted by two fangs, and have quinque-cuspid crowns, 

 the middle molar being the largest. 



According to this homology, the dental formula of the genus 

 Talpa is — 



.3.3 1.1 4.4 3.3 



The teeth are equal in number, and alike in both jaws ; the true 

 molars are reduced to the normal quantity in the placental series, 

 and the entire dentition is the least anomalous of any which is 

 manifested in the family Talpidce. 



The transition from the Moles to the Shrews seems to be made 

 by the Water-moles (My gale) and the Solenodon. The latter 

 insectivore combines the form of a gigantic Shrew, with a denti- 

 tion resembling that of the Chrysochlore. Each premaxillary 

 bone contains three incisors, the first large, canine-shaped, grooved 

 anteriorly, with the point inclined backward ; the other two 

 incisors small, with simple conical crowns ; these are succeeded 

 by seven teeth, the two anterior having three-sided conical 

 crowns, the other five bearing, in addition, an external' tuber- 

 culate basal ridge. In the lower jaw, the anterior incisor4s"verv 

 small, and the second large and laniariform, as in Scalops, but it 

 is remarkable for a deep longitudinal excavation upon its inner 

 side ; the third lower incisor is small and simple. Of the seven 



