MAMMALIA KODENT1A . 265 



chiefly to the species occurring in Russia, with a survey of the systematic 

 arrangement of the species iu general, their affinities and geographical distri- 

 bution, have been communicated by Braiidt, iu the ' Bullet de la Classe 

 Phys. Math, de 1'Acad. de Putersb.' ii, 1811, p. 209. Brandt first of all 

 divides the family of Jerboas into three sub-families : (1) Dipodina s. Tyla- 

 rodactyli ; (2) Merionina, (including merely the North American Jaculus) ; 

 (3) Pedctina. He again divides the Dipodina into two sections with three 

 genera, besides sub-genera and genera below these, as follows : Sect. A. 

 Dentes mcisorii superiores sulcati; pedes postici tridactyli Dipodes genitini. 

 Gen. I. Dijjits, Fr. Cuv., with two subgenera. 



Subgeu. 1. Scirtojwda, Brandt : molares jj molarium superiorum primus 

 facia exterua 2-3 plicatus, interim biplicata ; secundus et ultimus facie 

 utraque biplicati, &c. Pedum posticorum digitus medius lateralibus fere 

 subsequalis vel paulo lougior, articulo suo apicali laterales supcraus. Dentes 

 incisores albi. (a.) Hal fiats, Braudt : molarium sup. primus extus triplicatus, 

 intus biplicatus ; secuudus et tertius utrinque biplicati. Maudibuke niola- 

 rium primus et secundus utrinque triplicati, &c. Tail without black arrow-like 

 marking and white tip. As a species Brandt here reckons simply D. Tel urn, 

 Licht., and is of opinion that D. halticus, 111., which is based solely upon 

 Mus Jaculus, var. media of Pallas, likewise belongs here, on which account 

 Braudt would have the name, D. halticus, retained for this species. The 

 Reporter finds this restriction to be in the highest degree hazarded, since 

 Pallas unites his var. media with the Jaculus, and thus with a pentadacty- 

 lous species, while, with his usual accuracy, it is difficult to assume that he 

 should have committed an oversight upon this point, (b.) Haltomyx, Brandt : 

 molar sup. 1, 2 et 3 utrinque biplicati. Maudibulce molarium primus 

 utriuque biplicatus, secundus extus triplicatus, hit us biplicatus, &c. Tail 

 with arrowy marking. Here come 2, D. eegyptius ; 3, D. Idrtipes ; 1, 

 D. macrotarsus ; and 5, D. mauritanicus. The two latter species Brandt 

 considers, with the Reporter, to be insecure. 



Subgen. 2. Dijms, Brandt : molares *, molar sup. primus minimus simplex, 

 cseteri extus sub triplicati, iutus biplicati, &c. Pedum posticorum digitus 

 medius lateralibus augustior, longitudiue iis sub^qualis vel vix brevior. 

 Dentes iucisores auraiitiaci. Ex. 6, D. sagitta ; 7, D. layopus. Sectio 

 B. Deutes iucisorii superiores laevigati ; pedes posteriores 5-dactyli, rarius 

 4-dactyli. Scirtetides.Gen. II. Scirtetes, Wagn. : dentes molares -:}, cauda 

 pictura sagittiformi oruata. Subgenus 1. Scirtomys, Brandt : pedes postici 

 4-dactyli. 1, Sc. tetrad actylus, Licht. Brandt has unfortunately been 

 unable to impart any information concerning the osteology and dental sys- 

 tem of this remarkable species. Subgcnus 2. Sdrtela, Brandt; pedes 

 postici 5-daetyli. Here belong 2, Sc. Jaculus, of which Brandt distin- 

 guishes the following varieties : var. a. Macrotis = D. Juculiis, Auct., U 

 subvar. a. nigricans = D. decitmani(s,Tuickt., subvar. j8 flavesceus = D. ce.v- 



