1908. J DR. KNUD ANDERSEN ON BATS. 211 



works against the postei-ior margin of cusp 4 and the anterior 

 margin of cusp 5 of the lower m^, cusp 5 against the posterior 

 margin of cusp 5 of m^ and the whole of cusp 4 of m^. At the 

 antero-internal corner of the heel of m^ (at level with the lingual 

 margin of the heel of p^) is seen the low, but strong, triangularly 

 projecting cusp 6 ; it fits into a dej)ression in m^, immediately 

 behind cusp 2 of this latter tooth, and has checked the groAvth of 

 cusp 3 of m^, which consequently has become quite rudimentary. 

 The large postero- internal, inwardly projecting lobe of m^ repre- 

 sents cusp 7. The whole lingual portion of m\ bordered externally 

 by cusps 4 and 5, in front by cusp 6, internally by the lingual 

 margin of cusp 7, and behind by the very low posterior margin of 

 the tooth, forms a lai'ge crushing surface, the enamel of which is 

 densely wrinkled and extends on the lingual face of cusps 4 and 5 

 almost to their tips, thus forming an " inner cingulum " to these 

 cusps. This crushing surface consists chiefly of two concavities ; 

 the one, bordered externally by cusps 4 and 5, internally by cusp 6, 

 wears against the whole posterior portion (cusps 3 and 5) of m^ ; 

 the other, immediately behind cusp 6 and the somewhat project- 

 ing antero-internal margin of cusp 7, is acted upon by the high, 

 slender, conical cusp 2 of ni„. 



'»r (text-figs. 41 A, c). — Broader than long, but not so broad as 

 m^ ; the elements are the same as in m\ but their arrangement 

 somewhat difi'erent. Cusps 4 and 5 strong, but much lower than 

 in m^. The shape and size of cusp 4 is determined by that portion 

 of the lower m^ against which it has to work, viz., the hinder 

 margin of cusp 4 and the front margin of cusp 5. Cusp 5 is not 

 (as in m^) situated in a line immediately behind cusp 4, but has 

 moved to the middle of the posterior margin of. the tooth, where 

 it forms a strong, backwardly projecting tubercle ; this shifting of 

 the position of cusp 5 has been necessitated, because it has to 

 work against the hinder margin of cusp 5 of m^ and the small nig. 

 Cusp 6 has almost exactly the same position, shape, and size as in 

 m^ ; it acts upon the anterior and external face of cusp 3 of m^. 

 Cusp 7, which in m^ is so enormously developed, is in m^ quite 

 small, represented by a low, but perfectly distinct shelf at the 

 postero- internal corner of the tooth ; its small size is easily under- 

 stood when seeing that it has to work only against the posterior 

 margin of cusp 3 of m^ and the front of the very small m . The 

 median portion of m^ forms a large crushing surface, the enamel 

 of which is densely wrinkled, as in m\ and produced into a distinct 

 inner cingulum to cusps 4 and 5. This crushing surface is deeply 

 hollowed out in the middle, owing to the strong pressure of the 

 whole posterior portion (cusps 3 and 5) of m,. 



7)1? (text-figs. 41 A, c). — Rudimentary, as small as a lower incisor 

 (scarcely ^ the size of m^). The tooth has been pushed postero- 

 internally to m'^, pressed into an angular emai'gination between 

 cusps 5 and 7 of this latter tooth ; its elements cannot be discri- 

 minated. Quite functionless the tooth is not ; its antero-internal 

 portion is acted upon by the posterior portion of the small lower 



