Cistella Gray, 1853 non Gistl, 1848, a Darkling beetle Argyrotheca is a genus of very small to minute lampshells (maximum 5 millimetres or 0.20 inches long).

Another most unusual specialization in both these genera, is that the eggs (or ovae) are retained in the enlarged nephridia that act as a brood pouch.

The fertilized ova develop into ciliated larvae with a feebly free-swimming life of at most a few days before settling and metamorphosis into a tiny brachiopod fixed to the substrate.

Extant brachiopods with brood pouches (Megathyridoidea: Argyrotheca and Joania, Gwynioidea: Gwynia, and all Thecideoidea) are very small or minute and have short lives (2 years reported for A. cuneata [6]).

Three types of hole were distinguished, neat regular borings by a mollusc radula, large irregular ones presumably made by crabs, and bowl shaped hollows with a small opening at the bottom, characteristic for foraminifers.

[9] Another study of fossil A. cuneata showed a large difference between two nearby (2 km) and almost contemporary (Middle Miocene, Serravallian) locations in Poland.

[12] A. cistellula is a minute brachiopod, dirty white to yellow or grey in color, and has a maximum size of 2 x 3 mm.

This species attaches itself to hard substrates, in water between 20–100 m. The current known distribution of A. cistellula is Norway, the United Kingdom and Ireland (north-east Scotland, English Channel, west coast of the British Isles), and Italy (Sardinia and Sicily).

[13] Living specimens of A. cuneata have been reported from a submarine cave in Cyprus (Cape Greco, 6 m deep, with two other brachiopod species: Novocrania turbinata and Megathyris detruncata), and the Cape Verde Islands (Tarrafal, northwestern coast of Sao Tiago Island, 15 m deep).

[8] The species is also reported from the outer shelf (100–200 m deep), off the coast of Brazil (Rio de Janeiro, São Paulo, and Parana states), on carbonate rich sediment, where they are attached to shell fragments like those of bivalves.

[3] A. jacksoni is known from the Red Sea (shallow reef cave at Ras Muhammad, southernmost Sinai Peninsula, Gulf of Aqaba and around Port Sudan) and the Persian Gulf (Karan Island, 27°43’N 49°48.8’E; Jana Island, 27°22.4’N 49°54’E) from a depth between 5 and 16 m. It is close in size and shape to A. cuneata, which differs by having a pink-red wash between the costae.