346 Annals of the South African Museum. 



proximal, rounded: proximal sides longer than distal; madreporite 

 of liolotype, larger and much longer than the other shields, its 

 dixtnl sides nearly twice as long as proximal. (On the other spec- 

 imen, the madreporite is a trifle larger than the other shields but 

 is not otherwise peculiar). Adoral plates curved pentagonal, pointed 

 within where they barely meet, if at all, widest near middle and 

 extending down between oral shields and side arm-plates. Oral 

 plates small. Oral papillae, 5 on a side, of which the penultimate 

 is much the largest; it is tetragonal and much wider than long, its 

 width equalling the second and third together or even exceeding 

 them; the distalmost papilla is partly concealed, as it passes inward 



Fig. 3. Upper side of part of disk and arm of Ophiochiton australis 



sp. nov. x 10. 



above the big one; the distal papilla and a part of each of the big- 

 papillae are borne on the adoral plates, while the oral plates bear 

 the rest. No dental papillae. Teeth 5 or 6 in a column, tetragonal, 

 except the lowest which may be somewhat triangular. First under 

 arm-plates rather small, distally rounded and proximally prolonged, 

 decidedly longer than wide; following plates axe-head-shaped, at 

 lirst wider than long but soon becoming longer than wide, broadly 

 in contact; the distal margin is slightly convex and the lateral mar- 

 gins markedly concave. Side arm-plates rather small, projecting but 

 little and not meeting either above or below; each carries three 

 short, thick, blunt spines, of which the uppermost equals one arm- 

 segment, the middle one is a trifle longer, and the lowest nearly 

 equals the middle one. Tentacle-scale, single, large, oval, nearly 

 equal to the under arm-plate in length. Colour (dry) above light 

 dull brown, with a purplish-shade, more or less variegated, especially 

 on the upper arm-plates, with yellowish-white ; each radial shield 

 is whitish with a brown margin ; beneath, yellowish-white. 



