210 DR. KNUD ANDERSEN ON BATS. C^Pl'- '^' 



whereas in p'^ the heel is acted upon only by the pointed cusp 4 of 

 p^ ; the tij) of cusp 4 of m^ has made a deep, pit-like impression 

 on the heel of p^, just at the median point of the labial base of 

 cusp 5 ; also the high, slender, coniform cusp 2 of m^ rubs against 

 the heel of p^, viz., against its postero-internal margin, which by 

 this pressure is kept low and rapidly worn somewhat concave. 

 The anterior margin of the heel of p* is, like the cori'esponding 

 margin of p^, rather high, prominent, and sharp, for a similar 

 reason ; it fits into and works against the trenchant commissure 

 between cusps 4 and 5 of the lower p^ ; on the antero-internal 

 margin of the heel of p* is seen a small, but quite distinct, 

 triangular, rather blunt cusp, pi-oduced by the small cusp 5 (and 

 its commissure with cusp 4) of the lower p^ which catches and 

 works against it on its labial side. 



jOj (text-figs. 41 B, c). — Small, " diamond "-shaped, slightly longer 

 than high. The size and shape of its principal cusp (cusp 4) are 

 correlated to the size and shape of the triangular interspace between 

 the tip of p' and the upper canine ; cusp 4 and a rudimentary cusp 

 at the front end of the tooth (probably representing cusp 1) work 

 against the lingual face and cingulum of the upper canine and 

 the front margin of cusp 5 of p^. The hinder margin of cusp 4 

 (together with a small, pointed, straightly backwardly extending 

 prominence of the posterior margin of its base, perhaps repre- 

 senting cusp 5) work against the projecting anterior margin of 

 the heel of p^ The lingual cingulum of p^ is slightly expanded. 



p^ (text-figs. 41 B, c). — Viewed from the external side rather 

 closely resembling the upper p* in shape and size. Cusp 4 is 

 large, triangular, equilatei'al, by far the highest cusp in the post- 

 canine series ; it works against the lingual face and posterior 

 margin of cusp 5 of p^, the front margin of cusp 5 of p'^, and the 

 heel of p^, on which its tip has produced a deep depression. 

 A triangular emargination of the commissure between cusp 4 

 and the rudimentary cusp 5 (this latter situated at the postero- 

 external corner of the tooth) has been produced by the elevated 

 anterior mai'gin of the heel of p*, which fits into this emar- 

 gination. The small cusp 5 catches the labial side of, and 

 works against, the small antero-internal cusp on the front margin 

 of the heel of p*. The lingual, low, and cingulum-like portion 

 of the tooth is rather larger than in p^, chiefly owing to its 

 action against the front of the heel of p* ; there can be little 

 doubt that this lingual portion of p^, like the corresponding- 

 portion of p,, in fact represents the degenerated cusp 2 (com- 

 pare the lower premolars in insectivorous bats). 



m^ (text-figs. 41 A, o). — Enormously ex23anded in transversal 

 direction, its breadth being about Ig its length at the labial 

 margin ; considerably shorter at lingual than at labial margin. 

 Cusps 1, 2, and 3 have entirely disappeared. The external, tren- 

 chant margin of m^ is formed anteriorly by the triangular cusp 4, 

 rising to about half the height of the princijDal cusp of p"*, pos- 

 teriorly by the much lower, obliquely triangular cusj) 5 ; cusp 4 



