ECHINOIDEA. II. 183 



Dorocidaris papillata Echinus acutus Spatangus purpureus 



Cidaris affinis melo Echinocardium flavescens 



Diadema antillarum Paracentrotus lividus intermedium 



Centrostephanus longispinus Sphserechinus granularis mediterraneum 



Arbacia pustulosa roseus cordatum 



Genocidaris maculata Echinocyamus pusillus Brissus unicolor 



Parechinus miliaris Neolampas rostellata Brissopsis lyrifera 



microtuberculatus Schizaster canaliferus Metalia Costse. 



The Mediterranean region is characterized by the following species : Centrostephanus longispimts, 

 Arbacia pustulosa, Paracentrotus lividus, Sphcer echinus granularis, roseus, Parechinus microtuberculatus, 

 Echinus melo, Schizaster canaliferus, Echinocardium mediterraneum, intermedium and Metalia Costa. 

 Three of these species: Schizaster canaliferus, Echinocardium intermedium and Metalia Costce. are 

 hitherto known only from the Mediterranean (Sphcer echinus roseus it is better to leave out of consi- 

 deration, as its specific value 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 with Schizaster canaliferus 1 and Metalia Costa;, 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 survivors from its previous fauna. This is, at all events, the case with Sch. 

 canaliferus, which is known as fossil from the Miocene of Italy. 2 Mazzetti further records as occur- 

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

 prcssa, now known only from the American side of the Atlantic. On the other hand no Echinus-species 

 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 L,udwig (Echinodermen d. Mittelmeeres. p. 556) is shown by Fourtau (Contribution a 1'etude des 

 Echinides 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, Sphcerechinus granu- 

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

 pustulosa, Sph&rechinus granularis, Parechimis microtuberculatus and Echinus melo into the West 

 African tropical region, at least to the Cape Verde Islands. Finally Arbacia pustulosa also occurs 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 antillarum, Arbacia pustulosa, Genocidaris maculata, 

 Neolompas rostellala, Echinocardi^lm cordatum and Brissus unicolor.* Of these Diadema antillarum 



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

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



2 Mazzetti: Catalog! degli Echinidi fossili della collezione Mazzetti. Mem. Acad. Modena. 2. Ser. XI. 1895. 



3 The occurrence of Echinocardium jlavescens at the American Coast is not beyond doubt. 



