FRESHWATER AND LAND CRAYFISHES OF AUSTRALIA 
11 
Previous authors have referred the various species of this 
genus to Astacopsis Huxley, which is based on the Tasmanian 
Crayfish, A. gouldi sp. nov. (= A. franklinii Huxley, non 
Gray). Euastacus is separated from Astacopsis, as now 
restricted, by three important characters : 
1. The form of the gills. In Astacopsis (Plate I, fig. 2) the 
podobranclis have no broad wing-like expansion, and the 
stem is continued to the apex of the gill. In Euastacus (Plate 
I, fig. 1) the stems of the podobranclis are each laterally 
produced into a broad wing-like expansion, and the stem is 
not continued to the apex. 
2. The telson of Astacopsis is entirely calcareous, without 
trace of transverse sutures. The telson of Euastacus is mem- 
branous posteriorly, and more or less completely divided by 
a transverse suture. 
3. The abdomen of Astacopsis is smooth, except for four 
or five small spines on the pleura of the second abdominal 
somite. The abdomen of Euastacus, especially in adult 
examples, usually has three or more rows of large spines or 
tubercles laterally on each somite. 
Key to species of EUASTACUS gen. nov. 
Rostrum twice as long as broad at base. 
Abdomen shorter than carapace, furnished with three, sometimes four, 
rows of large sharp spines laterally on each somite. 
Second antennae reaching beyond end of telson 
SERRATUS (Shaw) 
Carapace and abdomen densely covered by short downy setae 
s.sp. HIRSUTUS (McCulloch) 
Abdomen as long as carapace, furnished with two, sometimes three, rows 
of large spines laterally on each somite. 
Second antennae reaching to third abdominal somite 
YARRAENSIS (McCoy) 
Rostrum one-fourth longer than broad at base. 
Abdomen longer than carapace, furnished with three sharp spines laterally 
on each somite; dorsum of first four segments raised to a large tumid 
ridge. 
Carapace studded with numerous small tubercles; six or seven large 
tubercles in an irregular row on dorsum of branchiostegites 
NOBILIS (Dana) 
Caranace sparsely studded with small tubercles on branchiostegites 
1 1 3 s.sp. KERSHAWI (Smith) 
Abdomen longer than carapace, without spines or tubercles, except on 
lateral margins FLECKERI (Watson) 
