DR. F. LEUTHNEll ON THE ODONTOLABINI. 



399 



series, like the teeth of a saw (woodcut, fig. 2, no. 1). If the mandibles are only 2 or 3 

 millim. longer, the teeth are di-sdded into two groups by a little gap rather beyond the 

 middle (no. 2). The gap is more distinct in no. 3, where the mandibles are only 

 1 millim. longer than in the preceding ; in no. 4 they become larger and larger, so that 

 the eight originally uniform teeth are divided into two series — one of five (subsequently 

 four) at the tip, and another of three at the base of the mandibles (forma amphiodonta). 



Eig. 2. 



3 2 1^ ? 



Modifications of the mandibles in Odontolahis alces, Eabr. 



2 ; no. 1 J , forma priodonta ; nos. 2-5, forma amphiodonta (cuminr/i, Hope) ; no. 7, forma mesodonta 

 (alces, Eabr.) ; no. 9, foima telodonta (dux, Westw.) ; nos. 6 and 8, intermediate connecting links. 



The three obtuse teeth at the base are at first uniform (cumingi, fig. 4), but in 

 no. 5 the first tooth has already become more prominent. The larger the mandibles, 

 the larger this tooth becomes by inward expansion, while the two teeth at the base 

 may remain. Among a number of specimens I found several which had only one small 

 tooth at the base (no. 6), while the more strongly developed central tooth projected 

 inwards and downwards like a conical appendage to the mandibles. In these large 

 specimens the five apical teeth are generally reduced to four (no. 7) ; at the same time 

 the mandibles become gradually more curved and rounded ; the tip only remains flat- 

 tened and compressed. If the last rudimentary basal tooth disappears, we get the true 

 mesodont form, in which a strong central tooth projects inwards rather beyond the 

 middle [alces, Fabr., no. 7). My materials from Manilla enable me to trace the 

 gradual and unbroken diflerentiation of the mandibles to this point. In the form 

 with longest mandibles [dux, Westw.) the middle tooth is entirely wanting (no. 9), 

 and we find nothing but the four small apical teeth (forma telodonta). 



