ECHINOIDEA. II. i8l 



certainly developed liere and appears as a tj'pical example of a species which has developed in au 

 isolated locality with very special physical conditions. It is quite in accordance with this that P. Jef- 

 frcysi is aniong the most specialized species of the gronp of Pourtalesiæ to which it belongs. 



The European boreal region coniprises the Atlantic littoral regions of Europe, from the 

 Chanuel to Northern Norway (East-Finmark), Iceland, Faroe-Islands and Great Britain; inclnding, of 

 conrse, both the North Sea, Skagerrak, Kattegat and the Baltic, as far as Echinoderms occnr there, 

 further the large platean along the Norwegian Coast as far out as to where the negative bottom 

 temperature occurs {the arctic abyssal region), which is very uearly coincident with the 500 fa- 

 thoms line. 



The littoral tract from the Chanuel to Gibraltar might thus far be reckoned to the boreal 

 region, as some of the species characteristic of that region also occur here; but ou the other haud 

 several of the species characteristic of the Mediterranean region extend aloug this tract towards the 

 Channel and the Southern Coasts of Britain. Thus two faunas meet here and intermingle, this tract 

 representing, in faet, a tran.sitional region. It is by the Malacologists generally called the Lusi- 

 tanian region or province; from an echinological point of view there is no reason to accept it as a 

 distinct region. 



The foUowing species are known from this region: 



Dorocidaris papillata Paracentrotus lividus Spatangus Raschi 



Parechinus miliaris Strongylocentrotus drobachiensis Echinocardium flavesceus 



Echinus esculeutus Sphærechinus granularis — peunatifiduin 



— acutus Echiuocyamus pusillus — cordatum 



— elegans Hemiaster expergitus — mediterraneuni 



— tenuispinus Brisaster fragilis Brissopsis lyrifera. 



— Alexandri Spatangus purpureus 



Of these species the foUowing are characteristic of this region: Parechinus miliaris, Ecliiiiits 

 csculciifiis. tcmtispiiius and Ec/iiitocardiiiiit pciinatifiduvi. The first named extends to the i\frican Coast 

 and perhaps a little into the Mediterranean. Fxh. csailnitus probably has its southern limit in the 

 Bay of Biscay. (The statements of its occurrence in the Mediterranean, at South Africa and Brazil 

 are probably all erroneous). Ecliinus tciiiiispimts is hitherto known only from the Porcupine Bank 

 and the Shetlands, Echiiiocardinii/ pouiatifidum is known from the F'aroe Islands to the Gulf of Gas- 

 cogne. (The statement of its occurrence in the Mediterranean has been shown above to be erroneous, 

 and i^robably also the statement of its occurrence at the American Coast will turn out to be due to 

 a confusion with another species). That these four species have originated within this region seems 

 beyond doubt. 



The followiug species are common to the boreal and the ]\Iediterranean region : Ecliinus aciitus, 

 Echiiiocyannis pusillus, Spatangus purpurc/is, Echinocardium flavesceus, cordatum and Brissopsis lyri- 

 fera. Most of them show a teudency towards developing a special Mediterranean variety, but the 

 characters are still upon the whole not very prominent. All these species have also been recorded 

 from the American Coast, but with the exception of Echinocardium cordatum, which seems to be 



