168 
HORN EXPEDITION—AMPHIBIA. 
little webbed, but in wliich individuals amongst certain species, which live under 
certain special conditions of environment, may develope a very strongly-mai'ked 
web. At the same time it may be pointed out that, so far as can be determined, 
precisely similar conditions of en\ ironment have not necessarily been accompanied 
in the case of allied species by a similar development in the matter of webbing. 
Thus Chiroleptes platycephahis and C. brevipalmatus will live side by side and 
burrow and testivate in the banks of the same water-hole, and yet, whilst the 
former is fully, the latter is not more than one-third webbed. Possibly the 
capacity of developing a strong web, which is undoubtedly of service in burrowing, 
has been one of the factors in determining the dominance of the species; at all 
events, C. platycephahis exists in far greater nundDers than its ally, C. brevi¬ 
palmatus. 
Distribution. —The distribution of this form is very wide, though the actual 
numbei’ of specimens hitherto secured is comparatively small. As Mr. Fletcher 
has noted in the case of Notaden bennettii., a great deal depends upon the season or 
time of year at which a search is made. 
In New South Wales Mr. Fletcher describes it as essentially an inland species; 
in Victoria ]\lr. Lucas has obtained specimens from both inland and coastal districts; 
and since then I have obtained several adults and a very large numljer of tadpoles 
from around Melbourne. Possibly this species is to be regarded as typically an 
inland form, with stragglers in the coastal region, as it appears to be essentially 
adapted to live in parts where a constant and abundant supply of water is not 
obtainable. In Central Australia it must be widely distributed, as we secui’ed it 
near Charlotte Waters, in the middle of the desert region at Ayer’s Rock, and 
again, a single small specimen at Darwent Creek, in the sand-hill country to the 
west of the McDonnell Ranges. 
Habits. —It appears to be essentially a burrowing form. During the Horn 
Expedition we only found in all two small specimens (not adult), and a few 
tadpoles in a small rock water-hole. The water at Ayer’s Rock is not permanent, 
and the nearest permanent water lies in the George Gill Range, eighty-five miles 
to the north, acro.ss the absolutely dry .sand-hills, in the midst of which lies Lake 
Amadeus. There can, therefore, be little doubt but that the tadpoles at Ayer’s 
Rock were the offspring of specimens which had passed through a drought seasf)n 
ajstivating in their burrows. 
The next heavy rains which fell after our visit brought out plenty of adult 
specimens in places where we had not previously, owing to the dryness, seen a 
