On the generic characters of Chirostyhs, with description of two Japanese species (Crustacea, Anomura)

The genus Chirostylus is one of the rare members in the Chirostylidae, in which 12 species are recorded. Of those known species 9 have been taken from the Indo-Pacific region and the other 3 from the Atlantic. The genus was monotypically established by Ortmann (1892), being based upon Chirostylus dolichopus from the Sagami Bay, Japan. Before this was described Ptychogaster by A. Milne Edwards (1880), the typespecies is P. spinifer from the West Indies. Subsequently, it was a subject of Bouvier (1896) to consider that the above two genera are synonymous, but he took Ptychogaster for available name in that report and his latter works in collaboration with A. Milne Edwards (1897) as well. In the same year (1896) Caullery pointed out that Ptychogaster A. Milne Edwards was preoccupied by the genus of Chelonia [ = Ptychogaster Pomel, 1847], and renamed for it as Gastroptychus. Afterwards, Ortmann himself (1901) admitted of their synonymity and assigned his Chirostylus for the valid name. Subsequent workers (van Dam, 1933; Chace, 1942, etc.) have all followed the Ortmann's conclusion. The five-segmented has been mentioned as an important part of the familial characters (Ortmann, 1901; Balss, 1957). As far as the Japanese Chirostylus is concerned, the details of the segmentation of that appendage have remained indistinct. Ortmann (1892) illustrated the antenna of Chirostylus dolichopus and stated that it consists of eight segments, the proximal third being the longest with a strong spine. From his study it was thought that the antennal peduncle is composed of three segments. Here were examined some of the specimens of Chirostylus dolichopus from the Sagami Bay deposited in the Biological Laboratory, Imperial Household, Japan, and a single specimen from Northern Kyushu, Japan which was described here as C. ortmanni sp. nov. An examination of the present material showed that both of the species lack