158 M.A.Milne-Edwards on the Group of the Mole-Eats. 



account of these resemblances they have been called Mole- 

 Rats. They are distributed into a certain number of genera, 

 such as BathyerguSj Georychus, Heliophobius, Spalax, Elobius, 

 and Siphneus. 



The group thus constituted is far from being natural, and 

 includes essentially distinct creatures. Thus I propose to 

 show that the Siphnei, commonly called " Zocors," really 

 differ much more than is generally supposed from the other 

 genera which I have just cited, and in the midst of which they 

 have been arranged. Their true place is beside the Voles 

 (Arvicolce). 



The genus Siphneus was established in 1827 by Brantz to 

 receive a species from Siberia, described by Laxmann under 

 the name of Mus myospalax, and figured by Pallas under that 

 of Mus aspalax. This new division was placed in the family 

 Cunicularia, by the side of Ascomys, Spalax, and Bathyergus. 



The zoologists who have subsequently occupied themselves 

 with the study of the Rodentia have retouched this classifica- 

 tion ; but for the most part they have placed the genus Siphneus 

 by the side of Spalax ; and F. Cuvier even united the species 

 in a single genus. He describes and figures the dentary 

 system, which really seems to authorize some such approxima- 

 tion ; but I have been able to assure myself that the skull 

 which served as a term of comparison for the zoologist just 

 cited did not belong to the Zocor or Siphneus myospalax 

 (Laxmann), but was derived from a Zemmi, Spalax typhlus 

 (Pallas), bearing a false determination. It was therefore not 

 surprising that so great a resemblance should exist between 

 the teeth figured by F. Cuvier, since they were derived from 

 the same species, and from individuals which only differed 

 from each other in age. 



This error, the existence of which no naturalist has suspected, 

 has been of great importance ; for it established close relations 

 between the Zemmi and the Zocor (that is to say, between the 

 genera Spalax and Siphneus) — an approximation which, since 

 that period, has been admitted in all treatises on zoology, and 

 in quite recent works we still see the characters of the dentition 

 of Spalax reproduced as belonging to Siphneus. 



M. Brandt, of St. Petersburg, is the only person who has 

 given an exact representation of the skull of this latter Rodent ; 

 but he persisted in placing it side by side with the Zemmis and 

 the genera Rhizomys and Bathyergus in the family Spalacidge. 

 In these latter forms the teeth are arranged according to the 

 same plan ; they are always furnished with roots, so that their 

 growth is not continuous, and the form of the folds of the 

 enamel is much modified according to the greater or less de- 



