108 INTRODUCTION. 



than the width of the mouth ; tail acutely 

 pointed, at least nearly twice as long as 

 the body . . . . B. esculenta. 



Interocular space but little wider than the 



distance between the nostrils or the width 



of the mouth ; tail once and two-thirds to 



twice as long as the body . B. arvalis. 



b. Series of labial teeth 3 -^- A . 



a. Tail obtusely pointed, once and a half to 

 twice as long as the body. 



Second series of upper labial teeth widely in- 

 terrupted in the middle; first series of 

 lower labial teeth at least two-thirds the 

 length of the second ; width of mouth a 

 little less than the interocular width, 

 which equals about once and a half the dis- 

 tance between the nostrils . B. temporaria. 



Second series of upper labial teeth continuous 

 or narrowly interrupted ; first series of 

 lower labial teeth at least two-thirds the 

 length of the second ; width of mouth 

 quite as great as the iuterocular space, 

 which equals about once and a half the 

 distance between the nostrils . B. grseca. 



Second series of upper labial teeth widely in- 

 terrupted in the middle; first series of 

 lower labial teeth hardly half as long as 

 the second; width of mouth much less 

 than the interocular space, which equals 

 nearly twice the distance between the 

 nostrils . . . . . B. iberica. 



(3. Tail acutely pointed or submucronate, 

 at least nearly twice as long as the 

 body. 



Interocular space once and a half the width of 

 the mouth or the distance between the 

 nostrils ; no tubercle on the upper man- 

 dible . . . . . B. latastii. 



Interocular space at least twice the width of 



