MAMMALIA. 677 



Saccomys F. Cuv. Incisor teeth smooth in front, molars 



4 4 



-j, complex. Buccal pouches external. Ears exsert, some- 

 what large. Feet pentadactylous ; pollex of fore feet short, with 

 nail small, flat. Tail elongate, annulate, thinly haired. 



Sp. Saccomys anthopkilus F. CUVIER, Mem. du Mus. x. pp. 419 428, PI. 26. 

 This animal, probably of American descent, is, apparently, known from 

 the description of a single specimen only. It differs entirely from Mus 

 bursarius with which FISCHER (Addenda,, Emendanda at Index ad Synops. 

 Mamm. p. 592) wished to unite it. 



Hesperomys WATERH., WAGN. Incisors smooth in front, 



3 3 



coloured ; molars ^ ~ , complex, with tubercles in two rows, the 



crown being entire, with folds of enamel more or less alternating 

 when worn. Ears moderate or somewhat large, exsert. Feet pen- 

 tadactylous, with pollex short, or the fore feet with hallucar wart 

 unguiculate. Tail moderate or long, with short hair or somewhat 

 naked. 



Until within a few years some species only of Mice from the New World 

 were known ; these have been since increased by many species, especially 

 from South America, which almost agreeing externally with the species of 

 the genus Mus, differ however from them altogether in the structure of the 

 molar teeth ; as has been shewn by WATERHOUSE Proceedings of the ZooL 

 Soc. v. 1837, pp. 15 21, and The Zoology of the Voyage of the Beagle, 

 Mamm. 1839. 



Sp. Hesperomys nasutus WATERH. Voyage of the Beagle, Mamm. PI. 17, fig. 

 2 ; Hesperomys hispidus, Oxymycterus hispidus PICTET, Notice sur les 

 animaux nouv. du Musee de Geneve, 2e Livrais. 1843, PI. 10 ; Hesperomys 

 elegans WATERH., Eligmodontia typus F. Cuv. Ann. des Sc. not., Sec. Se'r. 

 Tom. vii. 1837, p. 1 68, PI. 5; Hesperomys Darwinii WATERH. Voy. of 

 the Beagle, Mamm. PL 23; Hesperomys anguya, Mus anguya DESM., 

 PICTET 1. 1. 3ieme et 4ieme Livr. PL 15. 



Holochilus BRANDT. Upper lip not fully cloven, a fold of skin uniting 

 the fissure below. Sp. Hesperomys leucogaster, Mus (Holochilus) leucogaster 

 BRANDT, Mamm. exot. Musei Acad. Petropoli, 1835 (Mem. de I'Acad. de St. 

 Petersbourg, vi. Serie, Sc. math, et phys. Tome in. 2, Tab. 12). 



Rithrodon (Rheithrodori) WATERH. Upper incisors indented by 

 a longitudinal groove. 



Sp. Hesperomys cuniculoides, Reithrodon cuniculoides WATERHOUSE, The 

 Zoology of the Voy. of the Beagle, Mamm. PL 26 ; with two other species 

 in the most southern part of South America. 



