Cryptodromia tumida (English spelling)

...The Japanese name comes from the fact that they carry shells on their backs, but this does not happen in the wild. In the Pacific Ocean south of the Kii Peninsula and the Indian Ocean, there is an even larger species, Dromidiopsis dormia , with a shell width of 20 cm, but in rocky shores and shallow waters there are many smaller species, such as Cryptodromia tumida , C. canaliculata , Petalomera fukuii , and P. wilsoni , which carry sponges or colonial ascidians on their backs. In all of these species, the female's reproductive pore opens in the base segment of the second walking leg, just like hermit crabs (usually in crabs, it opens in the carapace), and they are considered to be the lowest of the crabs. ...

*Some of the terminology explanations that mention "Cryptodromia tumida" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…和名は貝殻を背負うということからついたが，野外ではそのようなことはない。紀伊半島以南の太平洋，インド洋にはさらに大型で甲幅20cmのオオカイカムリDromidiopsis dormiaがすむが，磯や浅海にはカイメンや群体ボヤを背負っているイソカイカムリCryptodromia tumidaやミゾカイカムリC.canaliculata，フクイカムリPetalomera fukuii，ワタゲカムリP.wilsoniなど小型種が多い。いずれもヤドカリ類と同様に雌の生殖孔が第2歩脚の底節に開口しており(ふつうカニ類では胸甲に開く)，カニ類としてはもっとも下等なものとされる。…

※「Cryptodromia tumida」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報