HORN EXPEDITION—AMPHIBIA. 
157 
The most important variation is concerned with the webbing of tlie hind-foot. 
In the British Museum Catalogue the species is described as having its “ toes 
rather short, one-third webbed, the webbing extended as a fringe to their tips.” 
The expression “ rather sliort ” may be applied to some but not by any means 
to all. It may be said with regard to the webbing that in the young forms 
(measuring about 8 mm. from snout to vent) that the description quoted above 
applies. Such young forms were found either amongst herbage on damp ground 
or under stones right by the side of water-holes. In them the webbing is developed 
to the same extent as in typical examples of L. sal/ninii, L. tasmaniensis and Z. 
dorsalis, and also in a medium-sized specimen of Z. ornatus which Mr. Fletcher 
kindly sent me from New South Wales. 
Z. ornatus is, however, a burrowing frog, and with the change in habit, 
occurring in the case of each individual, from life by or in a water-hole to 
burrowing in .sand comes apparently a change in the structure of the foot. 
The figures (PI. XV., Figs. 20-23), drawn from actual specimens, have been chosen 
to show the variation in the amount of webbing, which is carried to its greatest 
extent in a specimen from Palm Creek, in which a complete and fringed web may 
be described as present. This particular specimen liappens to be a male, but there 
is apparently no appreciable difiei’ence in the matter of webbing between the two 
sexes. 
In Fig. 21 I have drawn a foot in which the outer line of webbing refers to 
the extreme form met with in my specimen of Z. ornatus, while the lower dotted 
line indicates the least amount of webbing present in the same sjiecies, and also 
that which is present in specimens of Z. dorsalis, another burrowing species of the 
same genus ; in fact, the lower line indicates the amount of webbing which is usually 
present in this genus. 
With regard to colour the range of variation is very considerable. The species 
is described in the British Museum Catalogue as “olive above, marbled with 
darker; generally a light dark-edged cross-band between the eyes ; sometimes a 
light spot on the occiput; sometimes a light vertebral stripe, beneath immaculate.” 
In Fig. 3 is represented, as seen from the dorsal surface, what may be 
regarded as the typical pattern of the Central Australian foian. The most 
characteristic marking is a light lyre-shaped patch, the two limbs of which extend 
forwards, one on to each upper eyelid. In front of this is a somewhat T-shaped 
light patch, the cross-line extending over the anterior part of each upper eyelid 
