20 



stincte obsitis, illis internis auratis; caudd capitem corpusquc 

 fere arpuinte, pilis parce Icctd; suprd obscure fuscd, subtiis pal- 

 lidėfuscd; j^^dibtis fuscescentihus, digitis albicantihis ; mystaci- 

 busfusco-nigris : vellere brevi, molli; capite parvulo, brevi. 



unc. lin. 

 Longitudo ab apice rostri ad caudse basin . . 3 2 



cnudce 2 9 



ab apice rostri ad marginėm oculi . O 3į 



ab apice rostri ad basin auris .... O 7 



tarsi digitorumque O 9 



auris O 4| 



Hjec species mūri musculo appropinquat ; difFert attamen capite 



minore, (ratione ad magnitudinem habitą,) rostro bre-siore, tarsisąue 

 longioribus. 



Hab. Maldonado. 



Mus Maurus. M. pilis sulrrigidis, suprd purpurascenti-nigris, 

 subttis fusco-plumbeis ; capite fiisco-7iigro, rostrnfasco; aiiribi/s 

 parvulis sordidė albis, pilis ?ni?iutissimis pallidė fuscis obsitis : 

 cmuln corpusfere ccąnnnte, iiigrd, pilis sparsė vestitd: pedibus 

 fuscis ; mystacibus fusco-nigris, cid apicem grisescentilnis. 



unc. lin. 

 Longitudo ab apice rostri ad caudae basin ..11 3 



caudce 7 6 



ab apice rostri ad marginėm oculi . 1 



ab apice rostri ad basin auris .... 2 2 



tarsi digitorumęue I 8 



auris O 6^ 



HsEC species cblore mūri ratto appropinąuat, at purpurascenti- 



f usco tincta. Quoad staturam murem decumannm pergrandem ffeąuat ; 

 vėlius quoad texturam fere est ut in mūre decumano ; et ad basin 

 plumbeum ; pilis albis in dorso lateribusque intersparsis. 



Hab. Maldonado. 



" Though in the foregoing description I have retained the ge- 

 neric title Mus, I have here to statė that the above species natu- 

 rally divide themselves into several suborcUnate groups, the characters 

 of which are sufticiently evident, not only between themselves, but 

 also between each group and that to which the term 3Tus ought, I 

 conceive, to be restricted, and of -vvhich our common mouse {3Ius 

 musculus) may be regarded as the tyi:ie. To these groups I shall here 

 assign subgeneric titles, and at the šame time point out their chief 

 distinguishing characters without entering into any minute details 

 respecting thera, as I shall shortly have an opportunity of illustrating 

 my vievvs by means of drawings both of the teeth and of the animals, 

 without which it is impossible to convey a clear idea of the subject." 



Subgenus 1. Scapteromys*. 

 Molars with enamel deeply indented in the crown. In the front 

 molar of the lo\ver ja\v the enamel is indented t\vice on the outer 



* Scapteromyit, from S^^t-jij, a diggcr, and Mi/,'. 



