Rostrum a short, blunt and wide triangle, far overreached by the squarish eyes (almost with their full length). No antennal spine, but antennal angle low, broad and rounded. Antennular peduncle reaching with more than half the length of the third segment beyond the antennal peduncle.
Third maxilliped with merus and ischium strongly widened, forming an operculum; distal three segments all narrow, each three times or more longer than wide. Large chela in adult male with a deep concavity in the anterior margin of the palm just above the base of the fixed finger. Carpus about as long as the palm and slightly longer than high. Merus with a large, curved, bluntly rounded lobe in the basal part of the lower margin.
Telson quadrangular, longer than wide with broadly rounded posterolateral angles, without spines. Endopod of uropod broadly oval, only slightly longer than telson.
Type locality of Trypaea australiensis: "in oris Illawarrae Australiae orientalis" ( = mouth of Illawarra Lake, S. of Sydney, New South Wales, Australia). Types in USNM, now lost.
Type locality of Trypaea porcellana: "washed up at St. Kilda" ( = St. Kilda, 37°52'S 144°59'E, at present a district of Melbourne, Victoria, Australia). Two syntypes in NMI.
E. and S.E. Australia, from Townsville (N. Queensland) to Port Phillip Bay (Victoria). The most abundant Callianassid in E. Australia.
Habitat and Biology:
On intertidal sand- or mud-flats, often in or near estuaries. The animals burrow in the soft substratum.
Total body length 1.5 to 6 cm.
Interest to Fisheries:
In E. Australia the species is extensively used as bait for fishing. The so-called yabbie- pumps received their name from the Australia bait collectors, who were the first to use this suction pump for collecting these burrowing animals. As described by Hailstone (1962: 29-30) there are 3 types of yabbie-pumps (also called slurp guns). Two of these types are manual and are "essentially coring tubes, which, when pushed into the sand and extracted, remove a core of about 2 ft. [= about 60 cm] in length and from 2 in. to 4 in. [= 5 to 10 cm] in diameter. Either pump is then reinserted in the hole so formed and suction is applied (with the aid of a plunger in one model or by closing off all air outlets and withdrawal of the pump in the other model). As a results of this suction, water, sand and yabbies are drawn into the hole and removed " (Hailstone, 1962: 30). The third type is motor-driven and "works on the reverse principle, i.e., water under pressure is driven deeply into the sand and yabbies are flooded to the surface". The pump with the plunger is now used extensively in many parts of the world for collecting burrowing Crustacea from sandy or muddy substrates in the intertidal and subtidal zones as described by Manning (1975: 318-319).