HORN EXPEDITION NARRATIVE. 65 



thn ftiliirian Ranges wo now found thoni ;ilive in tlioir lionios from which in flood 

 tinios thoy ai'o waslied away down stream and ai'e loft strandod, wlion tho wators 

 dry up, in places where they cannot live. Thoy prefer the .shady sides of the 

 mountain ranges or of the gorges. In some cases, as Professor Tate remarks, one 

 species such as for example, Thenites adockiana (whicli was found in the Ilpilla 

 ravine) will bo more or less widely distributed, but in other cases there may be 

 only two or three colonies separated from each other by long distances. It is 

 perhaps a matter of some surprise that so many species of mollusea should be met 

 with in such a district as the dry interior of Australia, but though there is now 

 l)ut little ch;inco of its being stocked from without by carriage of tho anim;ils 

 across the dry I'ogions which everywhere separate the central rariges from tiie 

 moister coastal district, still there is no reason why a consi(lerabl(^ number should 

 not liaAO poi'sistod, some in moilitiod form, .as the descendents of a once lich 

 molluscan fauna. Water snails such as Limnoa, Mclania and Buliniis can always 

 lind sholtoi-ed water-holes amongst the ranges whore they can remain alive — if they 

 happen to be developed in them — during even th(^ driest season and from which \\\ 

 Hood times other pools can be stocked. Probably like most animals in this distiict 

 thoy have acquiied the power of leproducing the moment conditions are favourable, 

 and of de\eioping rapidly. 



The land forms of snail are more or less hardy, and by means of living as 

 they do in dchris around the base of and sheltered by thick trees such as the 

 native fig, growing on the shady side of hills, and by plugging up the mouth of the 

 shell to prevent desiccation they can withstand a dry climate in which at first it 

 might be thought that no land mollusc could survive. Naturally most of them are 

 of small size — some exceedingly minute — and not even the lai'gost of them is too 

 big to crawl into a small cleft and .so liid(^ itself during the hot season, protected 

 both by its position and its parchment-like operculum. Some of the water forms 

 a.s previously mentioned ( Isidotrlla iicwcoiidn) bui'row in the earth whilst the 

 hardiness of others (as Bitlii)iia australis) is shown Ijy the fact that with their 

 operculum tightly closed tliey can remain alive — quite dry — for at least fifteen 

 months. 



The floor f)f the gorge was rocky, and in the small water-pools amongst tho 

 deep clefts and amidst a rich growth of Vallisneria and Ohara were plenty of fish, 

 now so thickly aggregated that they could easily be caught by means of light 

 spears — an art in which the blacks were adepts. Most of them were bony 

 bream {C/mfocssii'i horiii)^ but none re^iched the size of those found in the deeper 

 pools such ,is the one at irenljury. 



