500 MURIDAZ—MURIN/® 
upper cheek-teeth of Cricetine (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 
(PIs XXVIL., Bigs). 
The presence of these three rows of tubercles in the upper 
molars of JZurvine is a fact of high zoological interest, and has 
given rise to much discussion. Some authors such as Tullberg 
(Wagethiere, 1899, 446) have regarded the inner row as a new 
addition to the mammalian molar. Winge (Vzd. Med. Nat. 
For. K7vb., 1881, 17, and 1882, pl. iii. fig. 10), 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 Murzne. 
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, Scz., xlii., 
203, 1893) and Forsyth Major (Proc. Zool. Soc., 1897, 714); 
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 m' of Afodemus (Pl. XXVIII, Figs. 
4-6, 7”) merely as a new offshoot from the postero-median 
tubercle—/zs cusp “5”; but Thomas (Azz. and Mag. Nat. Hist., 
January 1906, 84) has argued with right that, occurring as it 
does not only in Afodemus 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 J/zcrotzne, is numbered by 
Winge himself as “7” (Pl. XXVIII., cf Figs. 2-7). This view 
1 These are the cusps numbered 2” and 6 respectively in Pl. XXVIII, Figs. 4-10a. 
a 
