44 
TH. MORTENSEN, 
(Schwed. Südpolar-Exp. 
plus gros sur les ambulacraires; dix rangs, dont le médian de chaque côté plus gros 
sur les anambulacraires; les séries des plus gros tubercules convergentes vers l’ouver- 
ture inférieure; épines et auricules? Couleur de chair avec les tubercules verts.» 
»Cette espèce qui existe dans la collection du Muséum vient peut-être des mers 
australes, suivant M. de Lamarck.» 
It is perfectly clear from this description that this species cannot be identical 
with the margaritaceus of Agassiz; the tuberculation is decidedly different, as is 
also the colour. And the last remark proves beyond doubt that Blain VILLE has 
seen the type specimen, from which he evidently has made the description. In fact 
this description much more recalls a form like Sphcerechinus granularis. The fact 
that the species is placed in the genus Heliocidaris in Agassiz & Desor’s »Cata- 
logue raisonné» is also very much against A. Agassiz’ interpretation of the species. 
The type specimen having been lost, it is impossible now to determine with cer- 
tainty which species Lamarck’s Echinus margaritaceus was; it can only be said 
with certainty that it was not the species which A. AGASSIZ described under that 
name. The figures given by VALENCIENNES in the Atlas of the »Venus« do not 
help us to more certainty, the specimen having likewise been lost*; but they like- 
wise show with certainty that it is not the species called margaritaceus by AGASSIZ; 
especially the fact that there is a primary tubercle on every ambulacral plate is im- 
portant, the species called margaritaceus by AGASSIZ having a primary tubercle 
only on every second or third ambulacral plate. DöDERLEIN (Op. cit. p. 218) does 
not think it right to trust the correctness of VALENCIENNES’ figures in such details: 
»Ich glaube nicht, dass man aus der sehr schematischen Figur von Valenciennes mit 
Sicherheit einen Schluss ziehen darf, ob im Ambulacralfeld jede einzelne oder jede 
zweite Platte eine Primärwarze trug; mit dieser Annahme hat wohl Mortensen die 
Genauigkeit der farbigen Figur überschätzt.» I must object to this that it is not the 
coloured figure from which I conclude that VALENCIENNES’ Ech. margaritaceus has 
a primary tubercle on all the ambulacral plates, but from the detail-figures i.b. and 
I. c., which are not at all schematic, but evidently as exact and careful as any of 
the best figures of details of the test structure of Echini since published. In the 
detail figures of » Echinus pileolus » (PI. 9) it is very exactly shown that only every 
second ambulacral plate has a primary tubercle; there is then no reason to suppose 
that in the case of Echinus margaritaceus the figure should be so very incorrect, as 
it would be if it represented the species called margaritaceus by AGASSIZ. 
In short: we cannot any longer with certainty unravel which species was really 
meant with Lamarck’s Echinus margaritaceus ; but it is certain, from the descriptions 
* Even if this specimen were preserved, it would still be very questionable, whether it was really 
identical with Lamarck’s Ech. margaritaceus ; the tuberculation is not at all in accordance with Lamarck’s 
species, as described especially by Blainville. 
