Diagnosis
Currently this is the only genus in the subfamily Archiconchoecinae, so the diagnosis for the sub-family is applicable to the genus.
Species
Genus with 17 species, from which 7 known from UK waters.
Remarks
However, the wide diversity in characters shown by many of the species currently assigned to it, suggests that the genus should be subdivided. When Poulsen (1969) wrote his Dana Report he listed only four species. Then in 1978 Deevey described a further eleven, mostly from the Atlantic, and two more have been described from the North Pacific. Discovery material from the North Atlantic includes a further two undescribed species from very deep water and two sizes forms of A. cucullata that probably merit specific rank. The type species for the genus is A. striata, which is distinct in size (being very small), carapace shape, and numbers of claw spines on the caudal furca. The highly ornamented carapaces of the species similar to A. cucullata readily distinguishes them from the other species. A third group of species are characterized by having unusually short, stubby terminal setae on the fifth and sixth limbs. Thus the 18 currently described species (one of which is likely to be synonomous with another) together with the three undescribed species in Discovery material, should probably be subdivided into four genera.