412 

 CHAPTER VII. 



TEETH OF INSECTIVORA. 



The dental system is here remarkable for the many varieties 

 and even anomalies which it presents : almost the only characteris- 

 tic predicable of it in the numerous small quadrupeds which consti- 

 tute the Insectivorous order(l) being the presence of several sharp 

 points or cusps upon the crowns of the true molar teeth, which are 

 always broader in the upper than in the lower jaw. The teeth that 

 intervene between these and the incisors are most variable in form 

 and size, but are never absent : the incisors also differ in number, 

 size, and shape in different species, the anterior ones approximating 

 in some species to the character of the scalpriform teeth of the 

 Rodents. 



The Insectivora are divided into the families of Moles (Talpidee), 

 Shrews (Soricida), and Hedgehogs (Erinaceidce) , in which succession 

 their dentition will be here described. 



161. Talpida. — Of all existing Insectivora the Chrysochlore, 

 or iridescent mole of the Cape, makes the nearest approach, by 

 the number of its molar teeth, to that remarkable condition which 

 w^as manifested in the most ancient period of mammalian existence 

 by the extinct Amphitherium described in the chapter of Marsupialia. 

 We must assign at least gE^ true molars to the Chrysochlore (2) ac- 

 cording to their form, which, in the absence of the known order of 

 vertical displacement and succession, is the only character by which 

 the true and false molars can be defined. The anterior large lania- 

 riform tooth and the two succeeding small teeth are incisors, by 

 virtue of their position in the intermaxillary bones ; the next small 



(1) Pallas points out succinctly some of the leading diflferential characters which distin- 

 guish the Insectivora from the Carnivora or true Fei-ce in his ' Zoographia Rosso-Asiatica' where 

 (Vol. i. p. 119) he says " Continuitate etiam dentium, numero incisorum a Ferarura Ordine 

 semper discordante, caninis minus elongatis, plerumque uno alterove spurio stipatis, pedum 

 pentadactylorum structura multifaria et singulari, clavicularum perfectarum in sceleto prsesentia, 

 totoque indohs, morum, victus et habitus complexu, cuncta haec genera a feris omnino dis- 

 crepant, simul affinitate concatenata inter se successive cohaerent." The Insectivora are further 

 distinguished from the Carnivora by the absence of cerebral convolutions and by a discoid, 

 instead of an annular, placenta. 



(2) PI. 110. fig. I. 



