42 REPORT ON ZOOLOGY, MDCCCXLIII. 



than the body ; length ] 5 inches." Body 9" 4'", tail 6". He distinguishes 

 this species from M. rattus, by the dentition and the proportionate length 

 of the ears and tail. It evidently belongs not to Mus, but most probably to 

 llespcromys. 



Selys-Longcliaraps is now doubtful (Rev. Zool. 1843, p. 

 129) as to the identity, formerly asserted by him, of 

 Mus tectorum, Savi, and M. alexandrinus, Geoffr. 



In stating that he had obtained from the South of France Mu.t fectorutii 

 Savi, he adds : " this "Roof Rat, discovered by Savi in Tuscany, and simv 

 then found by Pictet, who named it M. leucogaster, at Geneva, appears to be 

 very common in the gardens of Provence. I believed it to be the same 

 species as M. ale.randrinus, Geoffr., but the specimen in the Paris Museum, 

 which I have accurately examined, appears to differ from M. tectorum in the 

 gray colour of the under portion of the body and of the feet, parts which 

 are pure white in M. tectorum." This remark is not exactly calculated to 

 clear up the matter, for whilst Selys makes M. tectorum and leucogaster 

 identical, Pictet had distinguished them specifically ; the belly also of 

 M. tectorum is stated to be usually not a pure white, but yellowish white. 



Numerous contributions to the further knowledge of the 

 Muriua, have been made by Sundevall in the K. V. Acad. 

 Handl. 1842, p. 217. 



In the first place he separates from Mus a genus, or rather subgeuus, 

 Isomys, which he thus distinguishes from the former : () that the lateral 

 hinder toes are of equal length, because the external, like the second toe, 

 reaches to the extremity of the metatarsus of the next one, whilst in the rest 

 of the Mice the external is much longer ; (1j) that the incomplete posterior 

 tubercle on the two first upper molars is wanting. To this genus Sundevall 

 refers Mtis rariegatus, Braiits, and a new species which he names Isomys 

 Irxtlcularis, with the diagnosis, "griseo flavcsceus, subtus labiisque albidus ; 

 rostri apice pallicle fulvo." Body Om. 15, tail 0.12. From Balir el Abiad. 



The three species of the subgenus Acomys are compared together at 

 length, viz. A. cahirinus, dimidiatus, and russatits (p. 222). He then 

 describes four species of Meriones, all collected, as well as the preceding, by 

 Hedcuborg. These species are (1) Meriones Gerbillus, Oliv. (uec Rupp.) 

 ' Magnitudine Muris musculi, macula ante et poue aures alba, cauda corpora 

 longiore, supra fusca, postice longius nigro-pilosa." Body 3" 4'", tail 

 without hair 4" 1'". Suudcvall places here Gerbillus (egyptiux, Desm. and 

 Fr. Cuv., but; excludes M. Gerbillus, Kiipp., which he unites with (lerbillti,- 

 )(i/i/<irt/t(x, which is larger. (2) M. eeintstus, n. sp. " Luteo-fuh us, gastnni 

 maculisque pone oculos et aures nivcis ; cauda corpora longiore, 



,v 



