ECHINOIDEA. II. 183 



Dorocidaris papillata Echinus acutus Spatangus pnrpureus 



Cidaris affinis — melo Echinocardiuni flavescens 



Diadema aiitillarum Paracentrotns lividus — intermedium 



Centrostepliamis longispiiiiis Sphærechinus granularis — mediterraneuni 



Arbacia piistulosa — rosens — cordatum 



Genocidaris maculata Echinocyamus piisillus Brissus iinicolor 



Parechinus iniliaris Neolampas rostellata Brissopsis lyrifera 



— microtuberciilatus Schizaster canaliferiis Metalia Costæ. 



The Mediterranean region is characterized by the foUowing species: Centrostephanus longispiiius, 

 Arbacia pustnlosa, Paracciitrotus lividus, Spliærechijins gra)iularis, rosens, Parcchinics inicrotiibcrculatus, 

 Ecliiniis iiiclo, Schizaster canaiiferus, Echinocardium nieditcrranciom, inter)nediitm and Metalia Costæ. 

 Three of these species: Scliizastcr canali/eriis , Echinocardium intermedium and Metalia Costæ are 

 hitherto known only from the Mediterranean [Sphærechinus rosens it is better to leave ont of consi- 

 deration, as its specific valne is not beyond doubt). Whereas Echinocardium intermedium may well 

 turn out to occur also outside the Mediterranean, being not so easily distinguished, this can scarcely 

 be the case witli Schizaster canaiiferus^ and Metalia Costæ, since they are so very characteristic that 

 it seems hardly possible that they can have been overlooked. It seems then certain that these species 

 have developed in the Mediterranean in earlier times, before the recent conditions of this sea were 

 arrived at, and are thus snrvivors from its previons fauna. This is, at all events, the case with Sch. 

 canaiiferus, which is known as fossil from the Miocene of Italy.^ Mazzetti f urther records as occur- 

 ring in the Miocene of Italy : Spatangus purpureus and Brissopsis lyrifera, as also Echinolampas dc- 

 pressa, now known only from the American side of the Atlantic. On the other hånd no Echinus-s^ecies 

 is recorded; it thus seems that Echinus acutus and melo must have immigrated from the Atlantic into 

 the Mediterranean after the formation of the Straits of Gibraltar. — The recent immigration through 

 the Suez Canal from the Red Sea of Heterocentrotus mamillatus recorded by Gauthier (160. p. 403) 

 and Ludwig (Echinodermen d. Mittelmeeres. p. 556) is shown by Fourtau (Contribution å l'étude des 

 Échinides vivant dans le Golfe de Suez. p. 414) to be very improbable. 



Centrostephanus longispinus is not known to occur outside this region, whereas the rest of the 

 species named above proceed into the adjoining regions: Paracentrotus lividus, Sphærechi/tus granji- 

 laris, Echinus melo and Echinocardium mediterraneum more or less into the boreal region, Arbacia 

 pustnlosa , Sphærechinus granularis, Parechinus microtuberculatus and Echinus melo into the West 

 African tropical region, at least to the Cape Verde Islands. Finally Arbacia pustnlosa also occnrs at the 

 Brazilian Coast. These species must probably all have originated in this region — and probably in the 

 Atlantic part of it — from which they have then spread more or less widely into the adjoining regions. 



The following species are common to the Mediterranean region and the East American region: 

 Dorocidaris papillata , Cidaris affinis, Diadema. antillaruin, Arbacia. picstulosa , Genocidaris maczilata, 

 Neolonipas rostellata, Echinocardi^im cordatum and Brissus unicolorfi Of these Diadema antillarum 



■ The record of the occurrence of this species at the American Coast of the Atlantic is caused by a confusion with 

 Sch. orhignyanus, as has been shown above, p. 117. 



2 Mazzetti: Catalogi degli Rchinidi fossiU della collezione Mazzetti. Meui. Acad. Modena. 2. Ser. XI. 1895. 



3 The occurrence of Echinocaydium flavescens at the American Coast is not beyond doubt. 



