OCR Text |
Show 712 DR. C. I. FORSYTH MAJOR ON THE [June 1, Tachyoryctes (in a lesser degree Rhizomys), Spalax, and Siphneus. In the great agreement between m. 1 and m. 2, there is a decided approach of Ncotomlnce to all these Old World forms ; there are species of Neotoma l in which scarcely any difference between 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 Muridae under consideration are on a lower level than the Neotomlnce. With the exception of Spalax they all have the jugal greatly ^ developed and approaching the lachrymal, whereas "in Neotomlnce the jugal is extremely reduced. Of the Hesperomiglnce with, a more complicated pattern there are likewise parallels in Madagascar, viz. Hallomys'2- 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 primitive condition than the simpler form, for reasons which will be fully discussed further on. Right upper molars of Nesomys rufics. Eig. 4. 6. 7. Right lower molars of Nesomys rufus. The molars of Nesomys figured in the text (text-figs. 3 & 4) represent 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 amongst Hesperomyince as " Hesperomys squamipes," 1 C. Hart Merriam, " A new Subfamily of Murine Rodents-\h%Neotomince7 Proc. Acad. Nat. Sci. Philadelphia, 1894, p. 240, fig. ha, b. 2 Since the above was written, I have seen in Leyden the type specimens of Hallomys audeberti, Jent., which proves to be a species of Nesomys. 3 Hensel, /. c. pl. i. fig. 24, pl. ii. fig. 14. |