220 J. Anderson — On the Suh-Genus Nesokia. [No. 4> 



more closed than in ordinary rats and mice, and in some of the more typi- 

 cal JSfesokice, such as M. (N.) hardwichii, they are almost closed. There is 

 also this further difference, that the palate of Mus-Nesohia contracts more 

 anteriorly than in Mus, and is always proportionally narrower, with a 

 much shorter edentulous interspace behind the last molar than in Mus. 

 In the larger rats, such as M. giganteus, the posterior portion of the 

 palate, in this respect, corresponds to Mus-Nesohia, and the features of 

 the palate generally are more Mus-Neso7cian, than those of true Mus. 

 The palate also of Mus-Nesolcia is marked bj^ two somewhat pronounced 

 longitudinal furrows which are the backward prolongations of the anterior 

 palatine foramina. These grooves, near their hinder extremities, have the 

 posterior palatine foramina lying in their course, and beyond them they 

 are prolonged over the posterior margin of the palatines where they nearly 

 constitute a closed canal by the inward projection of the inner palatine 

 border of the maxilla and the somewhat thickened and anteriorly recurved 

 posterior margin of the palatines. This arrangement is seen to occur only 

 in a very feeble degree in ordinary rats and mice which, however, have not, 

 as a rule, any thickening of the hinder margin of the palatines. Like the 

 majority of thoroughly burrowing rodents, tbe tympanies are relatively 

 much larger than in the ordinary rats. The large rats (Jf. giganteus) have 

 the palatine features and the tympanies of Mus-Nesolcia. These giant rats 

 have rather more elongated skulls than the more typical Nesokians and, 

 in this respect, they serve to connect the latter w4th the generality of 

 mice and rats, but in their other features they more resemble Mus-Nesohia 

 than Mus. I would therefore regard them as constituting a section of the 

 sub-genus Nesolda. This view was first put forward by 8ir Walter 

 Elliot, so long ago as 1839, and Blyth agreed with him in regarding the 

 affinities manifested by the great bandicoot rats as thoroughly Nesokian, 

 and in the propriety of separating all of these NesoTcian species from the 

 typical forms of mice. 



After a careful consideration of the characters which these various 

 species display, it appears that this sub-genus of Mus may be conveniently 

 divided into three sections ; 1st, one section containing such forms as Mus 

 {Nesohia) hardwicTcii^ M. (JSf.) huttoni, M. (N.) scullyi, the more typical 

 species of Nesokia, all characterised by broad incisors regularly laminated, 

 large molars and small anterior palatine foramina, with tails considerably 

 shorter than the body ; and the females possessing only 4 pairs of mammary 

 teats, two inguinal, one axillary and one pectoral : 2nd, another section 

 comprising M. (N.) providens, M. {N.) hlythianus (n. s.) and M. {N) bar- 

 clay anus {n. s.), distinguished by somewhat narrower incisors, smaller and less 

 regularly tranversely laminated molars, more open anterior palatine foramina 

 and longer tails ; with the females possessing as many as even 7 to 9 pairs of 



