44 TH. MORTENSEN, (Schwed. SUdpolar-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 infcricure; épines et auriculesr 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 niargarit accus of Ac^.ssiz; the tuberculation is decidedly different, as is 

 also the colour. And the last remark proves beyond doubt that Blainville has 

 seen the type specimen, from which he evidently has made the description. In fact 

 this description much more recalls a form like Spliœrecliinus gramilaris. The fact 

 that the species is placed in the genus Heliocidaris in Ag.ASSIZ &: Desor's jCata- 

 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 mai-garitaccus 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 niargaritaceus by AGASSIZ ; 

 especially the fact that there is a primary tubercle on every ambulacral plate is im- 

 portant, the species called viargaritaceus 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: 

 5>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 Vai,ENCIENNES' Ecli. niargaritaceus 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 i>Ec/iinus pilcolus-a (PL 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 Ecltimcs viargaritaceus the figure should be so very incorrect, as 

 it would be if it represented the species called niargaritaceus by AGASSIZ. 



In short: we cannot any longer with certainty unravel which species was really 

 meant with Lamarck's Echinus niargaritaceus: 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 £cli. margaritaceus ; the tuberculation is not at all in accordance with Lamarck's 

 species, as described especially by Blai.nville. 



