Ehrenberg, 1831
Mostly small slender monostiliferous hoplonemerteans in which the body wall musculature is not strongly developed; eyes usually distinct, mostly four arranged at the corners of a square or rectangle, occasionally fragmented; rhynchocoel extending to or almost to the posterior end of the body, with wall containing two distinct muscle layers; proboscis not strongly developed; frontal organ probably present; cephalic glands usually well developed but rarely extending behind the cerebral ganglia; cerebral sensory organs small, close to anterior margins of the cerebral ganglia; nervous system with neither neurochords nor neurochord cells, without accessory lateral nerve; blood vascular system with three longitudinal vessels, mid-dorsal vessel with probably one vascular plug; excretory system restricted to the foregut regions, with two or only a few nephridiopores; intestinal caecum present, with anterior diverticula; sexes separate; marine or estuarine.
Source: Gibson, 1982.
The following species of this genus occur in the region:
Tetrastemma candidum
Tetrastemma flavidum
Tetrastemma helvolum
Tetrastemma melanocephalum
Tetrastemma robertianae
Tetrastemma vermiculus