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Show 702 DR. C. I. FORSYTH MAJOR ON THE [Julie 1, (2) In Rhizomys, placed amongst the Muridae by Winge himself, the outer wall parts from the skull almost horizontally and is not only pushed forwards but upwards as well: this last Winge considers to be a secondarily acquired character1. And I think rightly; for in the closely related Tachyoryctes we meet with almost the normal Muridae-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 malar bone, Spalax appears to be on a higher level than the Dipodidae ; a circumstance which has not been overlooked by Winge 2. Whilst placing Spalax with some hesitation in the Dipodidae, Winge does not in the least insist upon a sharp separation of Spalax,Rhlzomys (and Siphneus), for he states expressly3: " Spalax, Rhizomys, 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 Rhlzomyes (Rhizomys and Tachyoryctes)4' are to be considered as low Muridae, and herewith I agree completely, Spalax has the same claims. In the comparatively powerful development of the malar bone, and in tbe form of the zygoma (considerable height of the anterior part), the Rhlzomyes, Tachyoryctes more than Rhizomys, occupy an even lower rank than Spalax. The outer wall of the infraorbital canal in Spcdax is scarcely less developed than in Cricetus. The pattern of the molars in Spalax, to judge from the youngest available stages, is the same as in Tachyoryctes and Brachyuromys, whilst it agrees somewhat less with Dipus,\vith which it is compared byWinge. 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 Spalax °; but the upper molars have three roots as iu Rhizomys and Tachyoryctes, two outer ones and a much larger inner one. They are far from being as hypselodont as in Tachyoryctes, being shorter even than in Rhizomys. Moreover, they are somewhat atrophied, very small, and of roundish contours ; the enamel-folds are rather superficial, so that tbe pattern becomes sooner simplified than in the two genera named. Some compensation is given by tbe thickness of the enamel bordering each molar. In correspondence with the much shorter molars, the maxillary bone, too, bas not acquired such a great vertical extent as it has in Rhizomys, and still more so in Tachyoryctes; but the presphenoid has followed tbe general elevation of the middle part of the cranium ; whilst remaining compact superiorly aud inferiorly, 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. 1 'Gnavere fra Lagoa Santa,' p. 124. 2 L. c. p. 121. 3 L. c. p. 167. 4 For Siphneus see below. 5 ' Craniologisehe Enfwicklungsstufen,' p. 215: " aile besitzen zwei kurze Wurzeln, eine hintere und eine vordere." |