Marine Investigations in South Africa, i. 1902, p. 224.
Cf. Sollas, Encyclopædia Britannica, 1887, art. "Sponges," and Schrammen, Mitth. Mus. Hildesheim, 14, 1901.
Sollas, Quart. Journ. Geol. Soc. xxxiii. 1877, p. 790.
Ridley and Dendy, Challenger Monograph, lix. 1887.
Ibid. p. 262; cf. also p. [197].