OBJECTIONS AND DIFFICULTIES AND OTHER THEORIES 205 



3. THE PRIMITIVE POLYP-I-NY THEORY. 



In a very interesting and exhaustive paper, On Souu' Miw< //> 

 Squirrels, with Jtfina,-/.-* on iln- Dentition a ml Classification oj the Sciuri/m 

 (p. 179), Dr. C. J. Forsyth Major, after a very careful consideration of 

 the simpler dental types in Rodents, concludes (pp. 196-215) with a 

 full discussion entitled "On the Primitive Type of Sciurine Molar and 

 of the Eutherian Molar in General." 



' Trituberculism," he observes, "or, as we rather ought to call it, 

 the reptilian-cone theory, is no more a theory, but has become a dogma. 

 I am a heretic, and may say that I opposed the theory already in 

 1873, viz. before it was invented; 1 since that time I have kept silent 

 for various reasons. ... It would appear that the Allotheria, the Multi- 

 tuberculata (p. 202), ought to have been a stumbling-block for the theory. 

 But this is not the case ; they have been simply pushed aside on account 

 of being an aberrant order. Nevertheless, I shall refer to them later on. 

 . . . The adherents of trituberculism assert that they have proved the 

 Mammalian molar to be traced back to a more and more simple form. 

 I have tried to show that they have failed to do so, and in my turn 

 assert that the molar of Placentalia can be traced to a polybunous form, 

 and that the real tritubercular pattern is a more specialized secondary 

 stage. So that, as a matter of course, the cardinal point to be estab- 

 lished is to show, that the more complex forms, which in the Lower 

 Eocene as well as in the recent period are found side by side with 

 the simpler forms, trituberculate or otherwise, are indeed the primitive. 

 the more generalized type." 



This point is supported by a detailed argument, of which we can 

 present merely a brief summary. The starting point is that (1) brachy- 

 odont teeth are more primitive than rootless or hy pselodont teeth ; ( 2 ) 

 that the more brachyodont a molar is the more polybunous it is. The 

 latter statement is illustrated by comparison of Eocene and recent 

 squirrels, in which the author observes that the most bracliyodnnt molars 

 exhibit flat, elongate crowns covered with small cusps which tend toward 

 a longitudinal arrangement. An example of this (Type 1) is Sciuro* 

 i adieu*. Type 2, Sciurus m It/a fix, which he believes represents a less 

 brachyodont successive stage, shows four more or less transverse ridges 

 with three intervening valleys. Type 3, AV/v.s getulus, a sub-hypsodont 

 squirrel, exhibits a more distinctly lophodont or crested crown, approach- 

 ing that of the more specialized Kodents. Again (p. 213), among the 

 New Guinea mice (Chiruromys), we find multicuspidate teeth "of a 



1 Forsyth Major, " Nageriiberreste aus Bohnerzen Siiddeutschlands uncl der Schweiz. 

 Nebst Beitragen zu einer vergleichenden Odontographie von Ungulaten uiul Unguiculaten." 

 1873, Palceontographica, XXII. 



