Title: Potamoid Crabs of the Ryukyu Islands? with Desrciptions of Five New Species (Crustacea, Decapoda, Potamoidea)
Abstract: Remarks, Morphologically this species is characterized by the following.1.The species is usually of small size, its biological minimum is about 20 mm in carapace breadth.2. The carapace and the cheliped bear tubercles and short striae.The propodus of the 2nd ambulatory leg is 2.0 times as long as broad ; the dactylus is stout.3. The merus of the third maxilliped is 0.7 times as long as broad.4. The penultimate segment of the first pleopod is straight.The ultimate segment is slightly curved outwards, and both the lateral sides is straight near the tip.The synovial membrane is 3.0 times as long as broad.This species is closely related to Geothelphusa sakamotoana, from which it may be distinguished by the above-mentioned characters.From G. dehaani, which is also very allied, it differs in having the tubercles on the dorsal surface of the carapace, in the proportion of the propodus of the legs, the gape of the fiww-s of the large chela and the shape of the first pleopod.Measurements.See Table 1.