Annotated type-catalogue of Brachyura (Crustacea, Decapoda) of the Muséum national d'Histoire naturelle, Paris. Part II. Gecarcinidae and Grapsidae (Thoracotremata, Grapsoidea), with an Appendix of pre-1900 collectors

Ngan mayla gen. et sp. nov, a new blind potamid cave crab from Borneo, Kalimantan (Crustacea: Decapoda: Brachyura: Potamoidea, Potamidae), and three other unidentified cave crabs from the same region

We here report on freshwater cave crabs of the families Potamidae and Gecarcinucidae in East Kalimantan, Sarawak, Indonesia in Borneo. A new genus and species of potamid crab, Ngan mayla, is described from Lubang Gedung Cave in the Merabu Karst. With its bullet-shaped eyes, Ngan mayla gen. et sp. nov. is totally blind and also displays the characters associated with an obligate cave-dwelling life, namely that it is dolichopod and fully depigmented. The closest genus and species is Cerberusa caeca Holthuis, 1979, from northern Sarawak. Highly modified, Ngan mayla gen. et sp. nov. proves to be among the most troglobitic of the known subterranean potamids, of which there were currently only seven in the Old World, with only four simultaneously being completely blind, entirely depigmented and dolichopod (Cerberusa caeca Holthuis, 1979, Diyutamon cereum Huang, Shih & Ng, 2017 and Phasmon typhlops Huang, Ahyong & Shih, 2020, to which must be added today Ngan mayla gen. et sp. nov.). Ngan mayla gen. et sp. nov. is easily distinguished from other potamid genera by its chelipeds bearing numerous acute teeth, spines (some horn-tipped) and short simple setae or spine-like setae on all articles. Two young female crabs collected in 2010 at the same area (Merabu Karst) but from a different cave, the Lubang Tebot Cave, could not be identified to specific level: an Isolapotamon sp., and a gecarcinucid with very long legs, pale colouration and slightly modified but black-pigmented eyes, close to Balssiathelphusa Bott, 1969, could possibly belong to a new genus. Some information on New World troglobitic crabs is provided.

Designation of a neotype for Orchestoidea tuberculata Nicolet, 1849 (Amphipoda: Senticaudata: Talitridae), a monotypic sandhopper endemic to the southeastern Pacific coast

The genus Orchestoidea Nicolet, 1849 is geographically restricted to sandy beaches of the southeastern Pacific coast of Chile, being found from 23S (Antofagasta, northern Chile) to 45S (Guamblin Island, southern Chile), along a latitudinal gradient of ca. 2,400 km. Orchestoidea tuberculata Nicolet, 1849, the only known species for the genus, was originally described from Valparaso Bay, central Chile (33S). However, the published morphological descriptions are incomplete and a comparison with populations along the entire distributional range is difficult, because the type material is considered lost. In this paper, we selected a male specimen recently obtained from a site close to the type locality, to designate a neotype for O. tuberculata. A detailed description and illustrations of this specimen are also provided to establish a basis for further analysis of Orchestoidea.