Genus Archisotoma Linnaniemi, 1912.
Isotoma-like species with a tridentate mucro in which two of the teeth form a pair side by side on basal portion of mucro. Bothriotrichia present. Sense organ on Ant. III with two clubs.
Archisotoma brucei Carpenter, 1906. Plate 50, figs. 185–186.
Clothing: Of short, plain setae with longer setae around Abd. VI.
Body: Length 1·75 mm. Antennae shorter than head. Ocelli six on each side. Postantennal organ elongate and narrow, longer than an ocellus. Abd. IV slightly longer than Abd. III.
Legs: Claw without any teeth. Empodial appendage needle-like with broad inner lamella for about half its length. No tenent hairs.
Furcula: Manubrium longer than dens. Mucro with strong apical tooth and a pair of larger, basal teeth.
This species was reported in New Zealand by Womersley in 1936 from Little Oneroa, Waiheke Island, where it was collected by Mr. E. D. Pritchard from amongst shore debris. The species was originally described from the South Orkney Islands, where it is stated to be very common.