REVISION OF AUSTRALIAN JERBOA MICE. 
did not define the meaning of the term nor explain his method 
of measurement. For this reason the angles of inclination of 
incisor teeth in all available specimens were measured during 
this investigation on a definite system and the results are noted. 
“Index of incisors’’ or “incisor index’’ used in this paper is the 
angle between two lines, one drawn through the centre of the 
external auditory meatus to the most anterior point where, in 
a true profile, the incisor joins the alveolar border ; and the 
other from the latter point through the cutting edge of the 
tooth. (Fig. 2.) 
Fig. 2. Angle quoted as index of incisors. 
Ears are measured from the notch at the base of the concha 
to the extreme tip of the ear. These and other measurements 
are tabulated at the end of the paper. 
Ridgway’s system for names of colours is used ( Colour 
Standards and Nomenclature) . 
All Australian Jerboa Mice, together with other Australian 
rodents, were included in the genus Hapalotis (Lichtenstein, 
1829) until 1892, when J. D. Ogilby (1) found that the name 
was pre-occupied ; he therefore replaced it by Conilurus, a 
name proposed by W. Ogilby in 1838. In 1898, E. R. Waite (2) 
in describing material collected on the Horne Expedition, 
separated the Jerboa Mice from the genus Conilurus on account 
of the specialisation of the pes, and erected two new genera, 
Thylacomys and Podanomalus, based on the presence or absence 
of a gular pouch ; he described the pouch as a rather shallow 
depression lined with fine hair, with the lower border thickened 
and of — v — shape. Waite (3) found that Thylacomys was a 
pre-occupied name and changed it in 1900 to Ascopharynx. 
Oldfield Thomas (4) in 1906 revised the classification and he was 
not prepared to accept the generic importance of the gular 
pouch ; at the same time he revived the name Notomys (Lesson, 
1842). In 1921, in revising the genus Notomys, he said (6) that 
the throat-pouch described by Waite would seem to be a skin- 
gland. Wood Jones (8) in 1925 reinstated Waite’s name, 
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