i84 



ECHINOIDEA. II. 



undoubtedly has its home in the East American region, but has crossed the Atlantic, its pelagic larvæ 

 having been transported b)- the streams. (It is true that the larva of this species is still unknown, 

 but the occurrence of the species on both sides of the Atlantic makes it almost beyond doubt that it 

 must have pelagic larvæ). Arbacia futsfiilosa, on the other hånd, has its home in the Mediterranean 

 region and has from there crossed the Atlantic to the Brazilian Coast. The course of the Gulf-Stream 

 from Florida to the Azores, and of the Northern Passat-Stream from West Africa to Brazil and the 

 West Indies naturally explains this extensiou of the two species in opposite directions. Echinocardium 

 cordatum probably also has its home at the European side of the Atlantic, where its main distribution 

 is; for the rest of the species: Dorocidaris papillata, Cidaris affinis, Genocidaris maculafa, Neolampas 

 rostellata and Brissiis 7tnicolor it is scarcely possible to state more preciseh', where their original home 

 must be sought for, as they seem to be equally widely distributed in both regions, the first of them 

 even ranging over the whole of the Northern Atlantic. 



The rest of the species occurring in this region, viz. Parcchimis viiliaris, Echinus acufiis. Ec/n- 

 cyamus pusillus, Spatangus purpurens, EckinocardiiDii flavcsccns and Brissopsis lyrifera are common to 

 this region and the European boreal region. Parechiniis viiliaris is certainly only an intruder from 

 the boreal region. The faet that Spafaiigus purpureus and Brissopsis lyrifera are found already in the 

 Miocene of Ital)- makes it rather probable that their original home is in the Mediterranean, from 

 which they have extended over a considerable part of the Atlantic, though probably not to the Amer- 

 ican side. For Echinus acutus, Echinocyamus pusilhts and Echinocarditim flavescens it is scarceU' pos- 

 sible to say more definitely which of the two regions must be regarded as their original home; it can 

 only be said that Echinus aculus has probably immigrated into the Mediterranean after the formation 

 of its recent connection with the Atlantic. 



The West African tropical region comprises the tract from Cape Verde and the Cape Verde 

 Islands to about the mouth of the Congo; it is, however, comparatively little known, and possibly its 

 Southern limit will prove to go somewhat farther down towards the Cape, the littoral fauna of this 

 Southern part of the African Coast being almost completely unknown. — Perhaps also St. Helena and 

 Ascension righth' belong to this region. Their littoral fauna is, however, too imperfectly known to 

 say anything certain thereof at present' 



The following species are recorded from this region: 



Dorocidaris nuda Echinus melo Echinolampas Hellei 



Cidaris tribuloides Sphærechinus granularis Echinoneus cyclostomus 



— metularia Tripneustes esculentus Schizaster Edwardsi 

 Tretocidaris spinosa — gratilla (angulosus) Brissus unicolor 



Diadema antillarum Echinometra lucunter Rhabdobrissus JuUieni 



Arbacia pustulosa Clypeaster subdepressus Metalia Africana 



Genocidaris maculata Rotula Augusti Meoma ventricosa. 

 Parechinus microtuberculatus — Rumphii 



I In the Report on the Fauna of Ascension (Ann. Mag. Nat. Hist. 5. Ser. VIII. 18S1) the following Echinoids are 

 named (identified by Professor F. J. Bell I: Cidaris metularia, Diadema setosum, Tripneustes angulosus, Echinometra sub- 

 am^ularis^ Echinoneus cyclostomus and Rotula dentata. It seems, indeed, very remarkable that no less than three Indo-Pacific 

 forms are represented in this locality, viz. Cidaris metularia, Tripmustes angnlosus f= gratilla) and Echinoneus cyclostomus, 

 and one can scarcely snppress a doubt, whether they are not really Cidaris tribuloides, Tripn. esculcjilus and Echinoneus 



