FRESHWATEK CRAYFISHES OK AUSTRAJ.IA. 



149 



north and west coasts. In the highland streams of the south 

 and centre a small form occurs (var. tasmanicus) which may or 

 may not be reckoned as a separate species (see p. 156). A. ser- 

 ratus (Pis. XVI.-XVIII.) occurs as a large form in the Murray 

 River and in the Paramatta River at Sydney. As a small or 

 medium-sized form it occupies the Victorian Highlands, and as a 

 small form it also occurs in the Blue Mountain streams. A. ker- 

 shaioi (Pis. XIX., XX.), which is, in many respects, intermediate 

 between the above two species, lives in a few Gippsland rivers, thus 

 occupying also an intermediate geographical station. The genus 

 Askicopis therefore runs from the mouth of the Murray River 

 southwards to Gippsland and Tasmania and up the east coast to 

 Sydney. Its centre of distribution would appear to be the Murray 

 River and its tributaries, and it is confined to the south-eastern 

 corner of Australia and to Tasmania, where the climate is tem- 

 perate and deal- swift-running streams are abundant. 



Text-fig. 18. 



Map of Australia show'ng areas of distribution of Crayfishes. 



The genus Ch^raps (see p. 165 and Pis. XXII.-XXIV.), 

 although departing in many important features from Astacopsis, 

 yet shows a trace of agreement with this genus, especially in the 



