702 DR. c, I. roESYTH MAJOR ON THE [June 1 , 



(2) In BMzorni/s, placed amongst the Muridse by Winge himself, 

 the outer wall parts from the skull almost horizontally and is not 

 only pushed forwards but upwards as well : this last AVinge 

 considers to be a secondarily acquired character '. And I think 

 rightly; for in the closely related Tach>/or)/ctes we meet with 

 almost the normal Muridse-type of the outer wall and the canal 

 itself. 



(3) In the powerful development of the maxillary process of 

 the zygoma and corresponding reduction of the mahir bone, S^xdax 

 appears to be on a higher level than the Dipodidse ; a circumstance 

 « hich has not been overlooked by Winge ^. 



Whilst placing Spcdtuv with souie hesitation in the Dipodidae, 

 Winge does not in the least insist upon a sharp separation of 

 iSj}aIa.i',Rhizomi/s (siiid Siplmeiis), for he states expressly ^ : " Spalax, 

 Rliizomys, and Siphneus are not widely separated animals ; they 

 take their origin from nearly related forms ; there is no very great 

 difference between a primitive Dipodide and little more or less 

 primitive Murides." 



The inevitable conclusion is, that if the Rliizomyes {ETiizomys 

 and Tachyoryctes)* are to be considered as low Muridae, and 

 herewith 1 agree completely, Spahix has the same claims. In the 

 comparatively powerful development of the malar bone, and in 

 the form of the zygoma (considerable height of the anterior part), 

 the Rliizomyes, Tcuhyoryctes more than Rhizomys, occupy an even 

 lower rank thau Sjtalax. The outer wall of the infraorbital canal 

 in Spalax is scarcely less developed than in Cricetus. 



The pattern of the molars in SpaJa.v, to judge from the youngest 

 available stages, is the same as in Tachyoryctes and Bntchyuromys, 

 whilst it agrees somewhat less with Dip us, with which it is compared 

 by Winge. The relative dimensions between m. 1 and m. 2 are as in 

 Tachyoryctes ; m. 1 is slightly larger. Brandt assigns two roots to 

 the molars of Spalcuv ' ; but the upper molars have three roots as 

 in Rhizomys and Tachtjot-yctes, two outer ones and a much larger 

 inner one. They are far from being as hypselodont as in Tachyo- 

 ryctes, being shorter even than in Rhizomys. Moreover, they 

 are somewhat atrophied, very small, and of roimdish contours ; 

 the enamel-folds are rather superficial, so that the pattern becomes 

 sooner simplified than in the two genera named. Some compen- 

 sation is given by the thickness of the enamel bordering each 

 molar. In correspondence with the much shorter molars, the 

 maxillary bone, too, has not acquired such a great vertical extent 

 as it has in Rhizomys, and still more so in Tachyoryctes ; but the 

 presphenoid has followed the general elevation of the middle part 

 of the cranium ; whilst remaining compact superiorly and interiorly, 

 its intermediate region has been transformed into a thin plate. 

 The basisphenoid has been transformed in a similar manner, as we 

 have seen to be likewise the case in Rhizomys and Tachyoryctes. 



' 'Gnavere fra Lagoa Santa,' p. 124. - L. c. p. 121. 



^ L. c. p. 167. * For Sipkneus see below. 



^ ' Craninlogische Entwicklungsst.ufen,' p. 215 : " alle besitzea zwei kurze 

 Wurzeln, eine liir.tcre und eine vordere." 



