712 



DK. C. r. FORSrTH ilAJOR ON THE 



[June 1 , 



Tachyoryctes (in a lesser degree Rhizomys), Spalax, and Siphnens. 

 In the ,c;reat ajfreemeut between m. 1 and m. 2, there is a decided 

 approach of Neotomince to all these Old World forms ; there are 

 species of Neotomn ' in which scarcely any difference betv^een m. 1 

 and m. 2 can be found. Of course this character, common to the 

 two groups, may be partly the result of both having hypselodont 

 molars. 



One important character in the skull shows that the Old 

 World Muridse under consideration are on a lower level than the 

 Neotomimv. With the exception of Spalax they all have the jugal 

 greatly developed and approaching the lachrymal, whereas in 

 Neotomince the jugal is extremely reduced. 



Of the Hesperomyincp with a more complicated pattern there are 

 likewise parallels in Madagascar, viz. Hallomys ^ and Nesomys. 

 These two genera will be more fully described on a future occasion ; 

 but I append here a short characteristic of the dentition of the 

 latter. I consider these complicated molars to be a more primiti^ o 

 condition than the simpler form, for reasons which will be fully 

 discussed further on. 



Fig. 3. 



Right upper molars of Kesomys rvfiis. 

 Kg. 4. 



Right lower molars of Nesomys rvfus. 



The molars of Nesomys figured in the text (text-figs. 3 & 4) repre- 

 sent the youngest stage 1 have been able to procure. In this stage 

 of wear the teeth are half-tuberculate, the outer tubercles in upper, 

 and the inner tubercles in lower molars being more cuspidate than 

 the inner tubercles of upper and the outer ones of lower molars. 

 In this as well as in other respects they approach nearer to 

 such forms VivaoT:\gst Hesperomyiiue as " Ifesj^eromys squamipes," ^ 



' C. Hart Merriara, " A new Subfamily of Murine Rodents— the Neoiamivce" 

 Proe. Acad. Nat. Sci. Philadelphia, 1894, p. 240, fig. 5o, o. 



- Since the above was written, I have seen in Leyden the type specimens of 

 Hallovtijs audeherti, Jeut., wliich proves to be a species of Nesomys. 



^ Hensel, /. c. pi. i. fig. 24. pi. ii. fig. 14. 



