KCHINOIDEA. II. 181 



certainly developed here and appears as a typical example of a species which has developed in an 

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

 frcysi is among the most specialized species of the group of Pourtalesise to which it belongs. 



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

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

 course, both the North Sea, Skagerrak, Kattegat and the Baltic, as far as Echinoderms occur there, 

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

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

 thoms line. 



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

 region, as some of the species characteristic of that region also occur here; but on the other hand 

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

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

 representing, in fact, a transitional 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. 



r 



The following species are known from this region: 



Dorocidaris papillata Paracentrotus lividus Spataugus Raschi 



Parechinus miliaris Strongylocentrotus drobachiensis Echinocardium flavesceus 



Echinus esculentus Sphserechinus granularis penuatifidum 



acutus Echinocyamus pusillus cordatum 



elegans Hemiaster expergitus mediterraneum 



tenuispiuus Brisaster fragilis Brissopsis lyrifera. 



Alexandri Spatangus purpureus 



Of these species the following are characteristic of this region: Parechinus miliaris, Echinus 

 esctilentus, tenuispinus and Echinocardium pennatifidum. The first named extends to the African Coast 

 and perhaps a little into the Mediterranean. Ech. esculentus 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). Echinus tenuispimts is hitherto known only from the Porcupine Bank 

 and the Shetlands, Echinocardium pennatifidum is known from the Faroe Islands to the Gulf of Gas- 

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

 and probably 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 following species are common to the boreal and the Mediterranean region : Echinus acutus, 

 Echinocyamus pusilhis, Spatangus p2irpurcus, Echinocardium flavescens, cordatum and Brissopsis lyri- 

 fera. Most of them show a tendency 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 



