ECHINOIDEA. 11. 



183 



Dorocidaris papillata Echinus acutns Spatangns pnrpureus 



Cidaris affinis — niclo Echiuocardium flavescens 



Diadema antillarum Paracentrotus lividns — intermedium 



Centrostephanns longispinus Splicer echinus grauularis — meditcrraiicum 



Arbacia pustulosa — rosens — cordatuui 



Genocidaris maculata Echinocyamus pusilhis Brissus unicolor 



Parechinus miliaris Neolampas rostellata Brissopsis lyrifera 



— microtubercnlatus Schizaster canaliferus Metalia Costce. 



The Mediterranean region is characterized by the following species: Centrostephanns longispirms, 

 Arbacia pustulosa, Paracentrotus lividtis, Sphmrechinus granularis, roseus, Parechinus microtuberculatus. 

 Echinus viclo, Schizaster canaliferus, Echinocardiimi mediterra^ieum, intermeditim and Metalia Costce. 

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

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

 deration, as its specific value is not beyond doubt). Whereas Echinocardium itttermcditcm may well 

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

 be the case with Schizaster canaliferus^ and Metalia Costce, since the\- are so \'er\- 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.^ Mazzetti further records as occur- 

 ring in the Miocene of Ital}' : Spatangus purpitrcus and Brissopsis lyrifera, as also Echinolampas de- 

 prcssa, now known only from the American side of the Atlantic. On the other hand no Echinus-s^^cx^?, 

 is recorded; it thus seems that Echinus acufus and iiielo 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 Four tan (Contribution a I'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 viclo and Echinocardium incditerraneuin more or less into the boreal region, Arbacia 

 pustulosa, Sphcerechinus granularis, Parechimis microtuberculatus and Echinus inclo into the West 

 African tropical region, at least to tlie 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 rostellata, Echinocardium cordatum and Brissus unicolor.T> Of these Diadema antillarum 



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

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



2 Mazzetti: Catalogi degU Echinidi fossiU della coUezioue Mazzetti. Mem. Acad. Modena. 2. Sen XI. 1S95. 



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



