Arbacia lixula var. africana Troschel
Family: Arbaciidae		Order: Arbacioida
Locality: unknown		Dimensions: 30 Ø x 15 mm
Key to the species of the genus Arbacia (acc. to Mortensen, A Monograph of the Echinoidea, II, page 566)
1.	A conspicuous naked zone in the interambulacra on aboral side. No conspicuous naked space.					2. 6.
2.	Colour of the denuded test greenish. Colour of the denuded test not greenish.					A. dufresnei, p. 579 3.
3.	Conspicuous red spots in interambulacra on aboral side. No red spots in interambulacra.					A. stellata, p. 575 4.
4.	Cleaned test reddish. Cleaned test not reddish.		A. lixula var. africana, p. 570 5.
5.	Inner interambulacral tubercles on aboral side conspicuously smaller than those of the adradial series (West Coast of S. America). Inner interambulacral tubercles on aboral side of the same size of those of the adradial series (East Coast of N. America and West Indies).				A.spatuligera, p. 577 A. punctulata, p. 573
6.	Test greenish. Test reddish, not greenish.			A. crassispina, p. 580 A. lixula, p. 566

Following this key the above urchin could easily be a true A. lixula africana. On the other hand Mortensen had a slight doubt, if the differences - the naked aboral interambulacral zone and the fewer tubercles in the horizontal series - would hold good compared with A. lixula. But, as the locality is unknown, I cannot be sure, that it is A. lixula at all. If one considers the test as "not reddish", it could be A. punctulata!