364 MICROTINiB 



closely allied species have been described, under the name 

 M. petemjii, from the Upper Pliocene of Beremend, Hungary, by 

 Prof. Mehely. 



Characters. — Size small, about as in M. newtoni. Cheek-teeth 

 with well-differentiated enamel; a little cement present in the 

 re-entrant folds. Lower cheek-teeth with the outer re-entrant 

 folds rather shallow, leaving noticeable confluencies between the 

 outer and inner triangles ; triangles distinctly alternating in j/ij. In 

 »!i (Fig. 99, 6, 6(7) the third outer angle has a well-developed prism- 

 fold, of which the anterior costa is a prominent feature ; external 

 vestige of the third outer valley distinct, but dying out upon the 

 side of the crown considerably above the level of the base of the 

 prism-fold ; inner portion of the third outer valley reduced, the 

 reduction probably being effected in the normal manner by the 

 conversion of this part of the fold into an enamel islet. Suppos- 

 ing it to exist at some stage of wear, this islet is a much more 

 ephemeral structure than it is in M. pliocce7iicus ; for no trace of 

 it remains in the type specimen, which belonged to a young 

 adult, for it has the beginnings of two large roots. In M. plio- 

 ccenicus of equal age insulation of the fold would have scarcely 

 yet been complete. Fifth inner angle obsolete. 



In the Hungarian remains upon which Prof. Mehely has based 

 his M. petenyii, m^ is very similar to the tooth just described, 

 and Mehely himself cites Newton's figure of my type in the 

 synonymy of his species. The only difference appears to be that 

 whereas the Enghsh specimen has a little cement in the re-entrant 

 folds, the Hungarian teeth lack it. Further material may 

 indeed show more important differences; but for the present 

 M. petenyii must be regarded as a synonym of M. reidi. 



The Hungarian specimens show that in the mandible the course 

 of the lower incisor is similar to that described above in M. plio- 

 cwnicus, and that the posterior root of m^ stands in a similar 

 relation to the shaft of the incisor. The palate closely resembles 

 that of the Hungarian specimen of M. plioccenicus ; m^ has three 

 roots as in the latter species, although the middle root is a little 

 more slender relatively ; but both m^ and )ii^ have only two roots 

 apiece. 



Remarks. — The tooth upon which M. reidi is based presents a 

 remarkable combination of characters; in it, confluency of the 

 dentinal spaces — a primitive character in voles — is coupled with 

 a highly specialized or reduced form of anterior loop and small 

 size. Although averse from describing species from single teeth, I 

 was not able to resist the temptation in this case, and the i r 

 opinion formed in 1907, when I first studied the type and only j (• 

 known English specimen, has since been confirmed by the dis- ii ] 

 coveries made in Hungary by Prof. Mehely. 



