BI 



IIANG TILL K. SV. VET.-AKAD. HANDL. BAND 13. AFD. IV. \:0 5. 105 



J, 2a/>. I <j, of Alexander Agassiz' Revision seems to come 

 very ne ar to tliis form. 



The opportunity I liave had of seeing autlientic specimens 

 of all the rarer species, induces me to make an attempt to 

 review tlie whole ffenus. In so doino- I shall follow the 

 elder Agassiz ') who made use of a character to which already 

 BlainA'ILLE called attention, and divide the Arbacise into two 

 groups, one for the species in which the adult bears spines 

 all över, up to the calyx, the »sixbgenus» Tetrapygus Agass., 

 and the other for the species in which the unarmed disks 

 form »a star>. the »subgenus» Agarites Agass. 



To the former of these groups pertain five species, which 

 from a careful comparison I think are severally distinct and 

 not to be united into one or two species. They represent 

 the Atlantic type of the genus, four of them inhabiting the 

 Atlantic coasts of the Old and New World, while one alone 

 has been found on the Pacific shores of America. 



By general agreement the Echimis tequitiiberculatus de- 

 scribed by Blainville in 1825 has been idcntified with the 

 only European now well-known species inhabiting the Medi- 

 terranean and the Eastern Atlantic, at the Canaiies, the Cape 

 Verde Islands and the Azorcs. In his Actinoloo-v, of 1834. 

 Blainville inserted a figure of it, which, no doubt by mistake, 

 was inscribed E. pustidosus, the name of one of the two very 

 doubtful Lamarckian species he had adopted, and which has 

 since been given promiscuously to four or five different species. 

 The Arbacia »quituberculatu Blv. difFers from the other four 

 in having, in the adult, the ambulacral tubercles so closely 

 contiguous as not to give rooni for an areola. 



The four specimens from which Troschel drew up the 

 description of his Echiiiocidaris africana are before me. As 

 appears from the dimensions he gives, a diameter of from 

 15 mm. to 22 mm., they are all young. They were coUected 

 on tlie Gold Coast by Finsch, and belong to the Museum at 

 Bonn from which they were kindly lent me by Professor 

 Bertkau. From Professor Edw. von Mårtens of the Berlin 

 Museum I received two specimens from Novo Redondo on 

 tlie coast of Loanda, presented by the German African Com- 

 pany, both marked with the same number, 2063. One of 



') Monogr. Scutelles, Obs. s. 1. progrus, p. 7. 1841. — C, R. p. 49, 1846, 



