Antennular plate with 4 strong spines, which are fused at their bases, forming a single bunch of 4 diverging points; anterior pair shorter than posterior pair. Exopod of third maxilliped present, with flagellum.
Transverse groove of abdominal somites with straight margins, not crenulated, usually uninterrupted.
Colour: body greenish or reddish, ranging from yellowish green through brown green to blue-black or dark reddish brown; speckled on carapace and abdomen with tiny whitish spots. No transverse colour bands on abdomen, but two rather large whitish spots on first somite. Antennulae not banded. Legs with wider or narrower longitudinal yellowish lines or streaks on a dark (greenish or reddish) background.
Type locality of A. penicillatus (and P. gigas, which is a replacement name for A. penicillatus): unknown ("Elle se trouve.....") Type material in Lamarck collection, in MP? In the Paris Museum there are 7 specimens of this species labelled "Mer des Indes", or without locality indication. One or more of these may belong to the type lot, but this cannot be made certain.
Type locality of P. ehrenbergi: "Coseir" (= Quseir, Red Sea coast of Egypt). Type in NMW.
Type locality of Cancer theresae: "At Tautira, in the barrier reef", Tahiti; whereabouts of type material unknown.
Indo-West Pacific and Eastern Pacific regions: Red Sea, E. and S.E. Africa to Japan, Hawaii, Samoa and the Tuamotu Archipelago and further east to the islands off the west coast of America (Clipperton Island, Revillagigedo Archipelago, Cocos Island, Galapagos Archipelago) and in some localities near the continental coast of Mexico (Sinaloa, Nayarit and Guerrero).
Habitat and Biology:
Depth range from 1 to 4 m, rocky substrates. In clear water, not influenced by rivers, often in surf zone and in surge channels. Therefore often near arid coasts and on small islands. The species is not gregarious and is nocturnal, hiding in the daytime in crevices in the rocks and coral reefs.
Maximum total body length about 40 cm, average adult length about 30 cm. Males usually much larger than females.
Interest to Fisheries:
The species is fished wherever it occurs. Mostly taken by hand or with spears during diving in daytime, or with torch light near the surface at night. Traps do not seem not to be very effective, but are used in places; trammel nets seem to give better results. On the west coast of Thailand the species is sold in local markets or directly to restaurants. In the Galapagos the average catch is 50 to 100 lobsters per day. They are sold fresh for local consumption or as frozen lobster tails.