Type species. Isarachnanthus maderensis (Johnson, 1861).
Diagnosis (sensu Carlgren, 1924). Arachnactidae with second couple of protomesenteries long, sterile with acontioids. Directive labial tentacle present. Arrangement of metamesenteries in each quartette M,B,m,b (1,3,2,4), more or less distinct.
Distribution. This genus is distributed worldwide.