of I he British Shrews. 29 



in the lower. Of the former, the last four on each side are Irue 

 molars, the second and third of which may be termed perfect, the 

 two others imperfect.* The second and third molars may be re- 

 garded as formed each of two triangular prisms, with their summits 

 directed inwards, oa which side there is a projecting spur or heel 

 at the base. In the second, the first prism is sensibly smaller than 

 the following one. In the third, the two prisms are equal. The 

 first molar is of a somewhat irregular form. Strictly speaking, there 

 is only the second prism present, of which the posterior side may 

 be regarded as excessively developed at the expense of the two other 

 sides, as well as of the projecting spur within. The first prism is 

 simply represented by a small point or denticle in advance of the 

 second. Viewed in profile, this tooth presents the appearance of a 

 sharpj^edge with threepoints, and resembles one of the false molars 

 observable in many of the Carnivora. The fourth molar is small, 

 and, like the first, formed but of a single prism. In this instance, 

 however, it is the first prism which is present, the second being ru- 

 dimentary, and exhibiting but one side, which is carried inwards to 

 unite with the projecting spur, which is itself also rudimentary. 



Between the molars just described and the two true incisors at 

 the extremity of the jaw, which last, from their peculiar develop- 

 ment, form a remarkable feature in the dental system of this genus, 

 are five small teeth on each side, concerning the exact nature of 

 which there has been much difference of opinion. Some authors 

 have regarded them as canines, others as false molars, others again 

 as lateral incisors. Without entering into the merits of this ques- 

 tion, which had already been discussed by M. Isidore Geoflfroy St 

 Hilaire,+ previously to Duvernoy's late memoir, I shall simply state 

 that in the present paper I adopt the opinion of the author last- 

 mentioned, who seems most disposed to regard them as iticisors, 

 principally from the circumstance of their being almost all implant- 

 ed in the intermaxillary bone.;}: I shall, therefore, continue to call 

 them, as some have done before me, lateral incisors, giving the 

 name of middle incisors to the anterior pair of teeth so remarkably 

 distinguished from all others by their form and great development. 



* In describing the molars, which appear to be nearly similar in all the spe- 

 cies, I have adopted, in a great measure, the language of Duvernoy. 



f See Diet. Class. d'Hist. Nat. Tom. ii. p. 313. 



\ One argument for not regarding them as false molars is founded by Duver- 

 noy on their relative proportions. He observes that false molars always in- 

 crease gradually in size from the first to the most backward. In the instance 

 of these teeth, on the contrary, the first in the series are the largest. 



