GERBILLUS AFER. 
Teeth, &c. Incisors of upper jaw rather slender, protruding about a 
me and a half beyond the alveoli , their points sharp and formed for cutting 
the anterior surface of each divided longitudinally by means of a deep and 
narrow furrow ; the incisors of the lower jaw about twice the length of those of 
the upper, moderately strong, and without a furrow. The first molar of the 
upper jaw is composed of three divisions, and the others of two, and each 
division, as seen in the crown of the teeth, resembles a flattened tube, with 
its edges in some almost in contact about midway between the outer and 
inner extremities, in others the distance between the sides is throughout 
nearly equal or even greater about their middle than at the extremi- 
ties. The hinder tooth is much smaller than the second, which again is 
considerably inferior in size to the first. The first and second molars of 
the lower jaw consist of the same number of divisions as those of the upper ; 
the third is entire, and in form is like one of the other divisions. The ossa 
nasi are 7\ lines in length ; the distance between the upper incisors and the 
base of the first molar six lines, and the length of a row of molars three lines. 
Specimens of this animal are to be obtained in abundance at the Cape of Good Hope, and 
there is no difficulty in procuring them even in the immediate vicinity of Cape Town. * It is 
known among the Colonists by the name of Nacht-muis, which appellation it has received 
from the circumstance that it rarely leaves its burrow excepting in the night, and that all its 
operations are carried on under the cover of darkness. It is commonly found in open plots of 
ground, which are clothed with a short grass, and situated in the vicinity of brushwood, and in 
such situations a number of individuals generally congregate and form their burrows, extend- 
ing them in different directions so as not to interfere with each other. The courses of the 
burrows are at first oblique, but after reaching into the soil to about a foot in depth, they com- 
monly run horizontally, and frequently are from three to four yards in length, and it sometimes 
happens that one intersects or communicates with another in its course. When 'young are 
about to be brought forth, a nest of soft grass is formed at the distal extremity of the subter- 
ranean passage, and in it they are placed until they are able to run about and provide for them- 
selves. The nacht-muis rarely continues for any great length of time in one situation; hence 
it may be considered as by nature a truly migratory animal. When it leaves one locality to 
take up its abode in another, it performs the journey during the night, and manages its time so as 
to be able to form a portion of its new habitation at least, before day-light appears. Specimens 
are most readily procured by digging in the course of the burrows, but care must be taken to 
ascertain that they arc actually inhabited at the time they are discovered, else much labour 
may be expended without an individual being captured. The ground immediately adjoining 
the holes must be closely examined; and if, on such examination, no recent footmarks can be 
discoiered, it may be inferred that they are the abandoned burrows, of some family which 
has taken up its residence elsewhere. 
