198 
W. A. HAS WELL. 
of tlie Murrumbidgee Eiver of the great Murray River 
system, which extends over all New South Wales with the 
exception of the narrow strip between the Dividing Range 
and the coast, over southern Queensland and a good part of 
Victoria aud a small part of South Australia. The range of 
Stratiodrilus would thus appear to be very extensive. So 
far, in continental Australia, I have found it only on the spiny 
crayfish (Astacopsis serratus), never on C hm raps bicar i- 
natus,^ on specimens of which, fi’om widely sundered localities, 
I have carefully searched for it. 
A re-comparison of Stratiodrilus with Hist riob della 
with the aid of Shearer’s paper and with the help of speci- 
mens of the European form,” shows that tlie two, though 
closely allied, are yet very distinct in a number of points. 
Stratiodrilus is a distinctly more highly-organised animal, as 
is shown in the more highly differentiated muscular and 
nervous systems, and in the presence of the three pairs of 
cirri with their sensory cilia. The excretory system of the 
two genera is widely different, as will be pointed out subse- 
quently. Other points of difference are the following : The 
tentacles in Histriob della are unjointed ; in Stratiodrilus 
they are all two-jointed. The anterior limbs are non-retractile 
in Hi striobdella; freely retractile in Stratiodrilus. 
Histriob dell a has no definite tail region; in Stratio- 
drilus this region is sharply marked off from the trunk, and 
its body-cavity is cut off from that of the latter by a parti- 
tion. A further difference lies in the position of the mouth, 
which in Stratiodrilus is further forward than in Histrio- 
bdella. 
The Australian form is nearly related to the Tasmanian. I 
^ In a useful and suggestive paper (‘ Proc. Zool. Soc.,’ 1912) on the 
Austrahan crayfishes, Geoffrey Smith proposes to sex^arate the hicari- 
nate crayfishes from the other smooth crayfishes under the new generic 
name of Parachaerax^s. 
* I found them common in Nex^hroxDS norvegicus. I have 
pleasure in thanking Prof. Cossar Ewart, Dr. J. H. Ashworth, and 
Prof. J. P. Hill for kind assistance. 
