REVISION OF THE GENUS EUASTACUS 
11 
It was not until 1866 that the species was described by von 
Martens (31), from a single female 330 mm. long, and named 
Astacus armatiis. In a later paper (32) he placed armatus 
with spinifer Heller as sjmonjTus of serratus Shaw. 
McCoy (16) referred to the species as Astacoides serratus 
and in a later paper (17) described in full detail and figured 
the species as serratus, and all following authors (with the 
exception of Faxon, who used spimfera) have referred to this 
species as serratus. 
Comparison of a large series of specimens from the Murray 
River with a series from Sydney shows that serratus and the 
Murray River species are distinct; therefore von Martens’ 
name armatus must be reinstated. 
Examination of material from the Murray River system 
has revealed two distinct species ; this fact was not recognized 
when my previous paper (2) was published. In that paper 
specimens from Echuca were accei^ted as typical, and were 
described and figured as serratus Shaw. These specimens, it 
has now been observed, agree in all characters with those 
found in the Goulburn River system and other southern 
tributaries of the Murray River, and in the IVIuri'ay River 
itself from Echuca west to Swan Hill ; but differ in several 
characters from those in the northern tributaries, in the 
southern tributaries east of Cobram, and in the Murray River 
itself east of Cobram and west of Swan Hill. 
The most outstanding differences between the two species 
are the length of the outer antennae, and the shape of the 
great chelae. In his description, von Martens states that “the 
hands are exactly similar in size and in the shape of the teeth 
situated on the cutting edges,” but he gives no indication of 
the size of the chelae or whether they are very slender or 
stout ; nor does he give any indication as to the length of the 
antennae. As a result of these omissions, it is not possible to 
.say which of the two species von Martens had before him. 
The habitat is given as Murray River, Australia. 
Since either of the two species will fit von Martens’ descrip- 
tion, it has been considered wiser to give the name armatus 
to the northern species, as this is the one that has been taken 
by the majority of previous authors as typical of the Murray 
River form. The southern species is redescribed herein as 
elongatus sp. nov., based on the specimens from Echuca which 
were previously, but erroneou.sly, identified as serratus Shaw. 
These are the specimens on which the genus Euastacus was 
founded; therefore the new species elongatus becomes the 
genotype of the genus Euastacus. 
