HORN EXPEDITION—MAMMALIA. 
25 
Two points will be noticed : firet, that the males (which are much rarer than 
the females) are larger than the latter, and, secondly, that there are somewhat 
remarkable variations in the size of individual specimens. 
The smallest mature male measures 136 mm. (head and body) in length, the 
largest 220 mm. 
The smallest mature female measures 125 mm., the largest 170 mm. That 
the smaller one is mature is proved by the fact that it is actually carrying young 
attnched to the teats. 
Apart from size, and a curious point with regard to the number of mammie, 
the larger agree precisely with the smaller ones, and it may be noticed that the 
three large ones were secured in June, after six months of very good season, whilst 
the rest were all secured at earlier dates. Dependent as these Central Australian 
animals are to a large extent upon the nature of the season for their food, it is 
possible that they attain full size at very varying pericxls of life, and that an 
animal reared during a successive series of bad seasons, and consequent dearth of 
food, may never attain the full size characteristic of the species, though at the 
same time it may bear young ones. 
A still more remarkable feature is to be noticed with regard to the numl)er of 
mammpe. 
In ten specimens the number is six, in three eight are present, and in one 
only four. 
In no case are there more than four to which, judging by their size, young 
ones have been attached ; in specimen y, with only foui’, these are all of large size, 
and have evidently I’ecently had young attached. 
In specimen f there are indications of two very small anterior mamnim in 
addition to the usual six ; whilst in specimens s and u eight are present, all small 
in size, as the animals were captured some months after the breeding season. 
Evidently the number of young produced at a birth is undei’going diminution, 
though whether this be a temporary or permanent reduction it is impossible to say. 
It is, however, worth noting that in both the large females caught after some 
months of exceptionally good season all eight mammai are equally developed. In 
two or three of those with only six, it is evidently the most anterior pair which 
have undergone retrogression. Possibly, as said above, two or three successive 
bad seasons, such as had actually occurred prior to the capture of the majority of 
the specimens, may have a very important direct influence upon the development 
of the body. 
