lin HORN EXPEDITION — NARRATIVE. 



Most of tlicso as niiglit lin,vo boon oxpoctod ai'O \vi(l(>ly distrihutod tlirongli tho 

 Ln.i'apintiiio rogion, l)ut of oiio spocios, Isidorclla navioiul>i, \vln(.-li is otliei'wiso 

 widely dist.rihutcd, we did not o1)taiii any specinions. 



With tlio land molluscs, which have no such means of distrihution as the 

 fr-esli water ones, tho case is very diflerent. As Professor Tate has pointed out, 

 and as was frequently impressed upon us whilst eollecting, they occur in voiy 

 contracted areas, sometimes as already noted in, for exaitiple, the cases of Angasclla 

 anigerciis a,nd Lijuxriis spcnccri we o)ily found single cohjnics. Out of a total of 

 twenty-five species secured during the expedition fourteen were found in and about 

 Palm Creek, of which foui', viz., Endodoiita plaiioibulina, CJiloritis squaiiiulosa, 

 Lipants spciiccri and Pupa Jicitl/iea, were found nowhere else. This remarkable 

 restriction of species to small ar'eas is veiy striking and is best exeniplided amongst 

 animals by the mollusca which, while they can pei'sist in sheltered spots, have very 

 little opportunity owing to climatic conditions of wandering far away from their 

 hiding }>laces and of estaltlishing themscKes elsewhere and so perliaps for long yea,i-s 

 a single colony will occupy a spot it may be only a few yards sfpiai'o. They are in 

 addition very liable to extinction, as when the rain falls it washes in tori-ents 

 down the cliff' sides on which they shelter, and as shown by the number of dead 

 sluills in the rejectamenta of the river all along its course nundjers must got 

 carried away and perish; just those which are in the cracks and crevices and most 

 sheltered spots alone being preserved. 



The pools were all full of clear water so that as usual tho Estherias wore dead, 

 but that they exist during the time when the water is muddy was shown by tho 

 presence of their dried carapaces in one or two spots where the pools had di'ied up. 

 There was only a single species (E. dictyon) to be found ; its carapace was slightly 

 more than an eighth of an inch in length, and wlion magniiied was scon to have a 

 raised network pattern ])etwoen the lines of giowth which had the appojir'ance of 

 cells of a honeycomb cut across. It is a now species and was only mot with in 

 this one spot, but in tho South Australian Museum are specimens of tlie same 

 species the exact locality of which is not known, though they serve to show that 

 it docs exist elsewhere. 



The Estherias are more characteristic of the pools m\ loamy flats as they prefer 

 muddy to clear watei', in fact as before said they do not seem al)lo to survive in 

 the latter, and as along tho Palm Creek there is very little sand or loam and the 

 water lies in clear rock pools the surroundings are scarcely suitable for them. 

 Around the edges of the pools little Ilylas (//! rubella) were found belonging to 



