Soo MURID^— MURINE 



upper cheek-teeth of Cricetince (see above, p. 383) have but 

 two rows of tubercles, but in their case the absence of a distinct 

 third row is due apparently to the slight development of 

 the median series, and not to a reduction of the inner row 

 (PI. XXVIII., Fig. i). 



The presence of these three rows of tubercles in the upper 

 molars of Murines is a fact of high zoological interest, and has 

 given rise to much discussion. Some authors such as Tullberg 

 [Nagethiere, 1899, 446) have regarded the inner row as a new 

 addition to the mammalian molar. Winge {Vid. Med. Nat. 

 For. Kjob., 1881, 17, and 1882, pi. iii., fig. iO(5), on the other 

 hand, homologises two of the inner tubercles with the cusps, 

 which he numbers as " 6 " and " 7 " ^ or the equivalents of the 

 "proto-" and "hypo-cones" of trituberculy ; he regards the 

 median and outer rows as simply the result of cleavage of the 

 outer tubercles which are normally present in mammalian molars 

 but which have been specially enlarged in those of Murinee. 

 What, for reasons which cannot be discussed here, is probably 

 the correct view of this latter matter has been put forward 

 independently by Osborn {Proc. Amer. Assoc. Adv. Set., xlii., 

 203, 1893) 3-nd Forsyth Major {Proc. Zool. Soc, 1897, 7^A)'^ 

 these regard the median row of tubercles as the enlarged repre- 

 sentatives of those molar elements which in other placentals 

 are called "intermediate "cusps, which comprise the "proto-" 

 and " meta-conules " of trituberculy. Both writers thus agree 

 with Winge that the inner row comprises ancient and normal 

 elements of the mammalian molar. Winge regards the postero- 

 internal tubercle of the w^ of Apodemus (PI. XXVIII., Figs. 

 4-6, " 7 ") merely as a new offshoot from the postero-median 

 tubercle — kis cusp " 5 " ; but Thomas [Ann. and Mag. Nat. Hist., 

 January 1906, 84) has argued with right that, occurring as it 

 does not only in Apodemus but in many quite distinct murine 

 genera now isolated in such remote corners of the Old World 

 as Australia, the Philippines, Celebes, New Guinea, and Africa, 

 this tubercle must be regarded as an ancient element also, and 

 not as a new addition ; and Hinton now homologises it with 

 the cusp which, in the teeth of Microtincs, is numbered by 

 Winge himself as "7" (PI. XXVIII., cf. Figs. 2-7). This view 



' These are the cusps numbered x" and 6 respectively in PI. XXVIII., Figs. 4-io«. 



