Lissothuria

Pawson, 1967

8 species

Small forms, sole 2 cm distinct sole with numerous feet in 3 crowded bands. Dorsal side with numerous small scales, lacking at the mid-line (except in young individuals), feet numerous and external layer of spicules well developed. Spicules in the sole perforated plates 0.1-0.15 mm and smaller flattened baskets 0.06 mm; feet with end plate and supporting rods. Dorsal side with scales and perforated plates 0.18 mm. In most individuals, a number of huge tower-like deposits 0.2-0.3 mm numerous in young individuals where the other types of external spicules may be scarce. Dorsal feet with rudimentary end plate and curved perforate plates or rods in the walls. Introvert and tentacles with perforate plates or buttons and rods. (Clark, 1938 for Thyonepsolus)

Psolids with tube feet on dorsal surface of body and in mid ventral interradius. Dorsal scales few or numerous, imbricating, covered by an external layer of deposits that include hourglass shaped bodies and towers; one of these types may be absent. Sole deposits are knobbed or smooth plates; in some species shallow or deep cups also present. (Pawson, 1967)