The genus contains some of the only species of spiders to have just four eyes along with some species of Caponiidae, to which they are not closely related.[6][7] The eyes are large and unequal in size, closely grouped around the center of the cephalothorax, with the eye group tending to be set further back in males. The genus contains some variation in eye arrangement, as Tetrablemma alaus, a subterranean species, lacks eyes or any eye spots entirely.[8] They have four closely positioned spinnerets enclosed in a corneous casing.[3]
Lehtinen divided the genus into three subgenera in 1981: Kumaonia, Indonops, and Tetrablemma, although this subgeneric arrangement is not always followed by subsequent authors.[9]
^Cite error: The named reference WSC_g3268 was invoked but never defined (see the help page).
^Brignoli, P. M. (1976). "On some recent papers about Indian spiders". Bulletin of the British Arachnological Society. 3 (8): 211–213.
^ abPickard-Cambridge, O. (1873). "On some new genera and species of Araneida". Proceedings of the Zoological Society of London. 41 (1): 112–129.