190 



ECHINOIDEA. II. 



Leaving aside among these all rare, inconspicuous or not easily recognizable species, we still 

 get a fair proportion of species peculiar to this region. It is certainly not likely that such species as 

 Dorocidaris Blakci ', EcJiinus gracilis, Clypcastcr latissimus , Ecliinolampas depressa, Conolaiupas 

 Sigsbci, Palcropncustes cristatus , Jiystrix, Linopucustcs loiigispinns , Agassizia cxccntrica , Periaster 

 limicola, Schizastcr orbignyanus and Macropneustcs spatangoides will ever be found to occur 011 the 

 European side of the Atlantic, as, on the other hand, it is equally unlikely that Porocidaris pur- 

 p 11 rata and Spcrosoma Grimaldi should prove to occur at the American side of the Atlantic. Thus 

 it seems beyond doubt that also the Atlantic Deep-sea has its definite regions. — It must, however, 

 be borne in mind that the distinction between littoral and deep-sea regions is mainly artificial, and 

 marked limits between the deep-sea regions, such as between the cold and the warm area in the 

 Northern Atlantic, do not exist. 



In the Blake s-Echinoidea (p. 79) Agassiz states that «the deep-sea Fauna of the Caribbean 

 and of the Gulf of Mexico is far more closely allied to that of the Pacific than to that of the Atlantic . 

 Though it may be emphasized that not a single species is common to the East and West Coast of 

 America, it is certainly beyond doubt that a rather considerable portion of the West Indian Echini 

 have been derived from the Pacific in previous times when Central-America did not yet exist. Such 

 genera as Diadcma, Psaiuiuccliiuus, Tripneustes, Ec/iiuoiucfra, Mellita, Encopc, Rhyncopygus, Agassizia, 

 Moira and Meoma are most probably of pacific origin. But on the other hand an even larger number of 

 genera are common to the West Indies and the African-European side of the Atlantic, but not known 

 from the Pacific Coasts of America, such as: Dorocidaris, Phormosoma, Calveria, Arcrosoiua, Hygrosoiua, 

 Trigouocidaris, Gciwcidaris, Echinus, Ec/iiuocyaiuus, Neolaiupas, Echinolampas, Pahrotropus and Ecliiuo- 

 cardium. Adding thereto the considerable number of species identical in the West Indian Seas and 

 the Atlantic, it seems not too much to say that the above quoted statement of Agassiz is very 

 exaggerated. 



To enter on a discussion of the geographical distribution of the whole of the Echinoidea 

 would carry us too far. I must limit myself to pointing out a few facts. 



The South African fauna is, as pointed out by Doderlein, remarkable through the mixing up 

 of Indo-Pacific with Atlantic species and not less for the peculiar resemblance to the European boreal 

 fauna. This resemblance, however, is not so great as hitherto supposed, because on a closer exami- 

 nation the South African forms have proved to be distinct species, or at least distinct varieties; scar- 

 cely any species of Echinoids (except the almost cosmopolitan Ecliiuocardium cordafitm) will prove to 

 be common to the South-African,- and the European boreal region. Nevertheless these corresponding 

 species: Spataugus Raschi — capcnsis, Brisastcr fragilis — capcn sis, Ecliiuocardium fiavcsccus — cape use, 

 Brissopsis lyrifera — capensis seem to point definitely to a direct connection of the two regions during 

 a former period. 



The antarctic and subantarctic seas evidently form a distinct region, characterized mainly by 

 the several species of Stcrechiuus and Aba fits. With the exception of Stcrccliiuus Ncuiuaycri they all 

 seem to have a rather restricted distribution, probably on account of their not having pelagic larvae 



