1 86 



ECHINOIDEA. II. 



Agassizia excentrica Moira atropos Metalia pectoralis 



Periaster limicola Macropneustes spatangoides Meoma ventricosa 



Brisaster fragilis Echinocardium cordatum Brissopsis elongata 



Schizaster orbignyanus Brissus unicolor atlantica. 



A considerable part (31) of these species exclusively belongs to this region, not occurring else- 

 where, viz. 



Dorocidaris abyssicola 

 Tretocidaris Bartletti 

 Aspidodiadema Jacobyi 

 Arbacia punctulata 

 Echinus gracilis 

 Paraceutrotus Gaimardi 

 Psammechinus variegatus 

 Echinometra viridis 

 Clypeaster latissimus 

 Ravenellii 

 Echinanthus rosaceus 



Mellita sexforis 



testudinata 

 Encope marginata 



Michelini 

 Echinoneus semilunaris 

 Echinolampas depressa 

 Couolampas Sigsbei 

 Rhyncopygus caribbsearum 

 Palaeotropus Josephinse 

 Palseopneustes cristatus 



Pala^opneustes hystrix 

 Ljnopneustes longispinus 

 Palseobrissus Hilgardi 

 Agassizia excentrica 

 Periaster limicola 

 Schizaster orbignyanus 

 Moira atropos 



Macropneustes spatangoides 

 Metalia pectoralis 

 Brissopsis elongata 



Several of these species also occur in the deeper regions, the limit between the littoral and 

 archibenthal zones being here especially arbitrary and not expressed in the bathyinetrical distribution 

 of the species. 



Besides the above named 31 species the following are also really characteristic of the region, 

 but have crossed the Atlantic, thus occurring in the Mediterranean or West African tropical region: 

 Cidaris tribuloides, Diadema antillarum, Tripneustes esculentus, Echinometra lucunter? Clypeaster sub- 

 depressus and Meoma ventricosa. Two species, viz. Salenia Pattersoni and Coelopleurus floridamis also 

 occur at South Africa; it is scarcely possible to say, where their original home is. 



Among the rest of the species occurring in this region one, Arbacia pustulosa, is an intruder 

 from the Mediterranean region, while the remaining are either widely distributed over the Northern 

 Atlantic, viz. Dorocidaris papillata, Brisaster fragilis, or at least common to two or more regions, viz. 

 Cidaris affinis, Trigonocidaris albida, Genocidaris maculata, Echinocardium cordatum, Brissus unicolor 

 and Brissopsis atlantica (?). Forj the present, at least,) it is impossible to say whether these belong 

 originally to one or the other of the regions. 



The Atlantic deep-sea regions. Though the physical conditions of the deeper regions appear 

 to be of a very uniform character over the whole Atlantic, it is evident that the Echinoids occurring in 

 the deeper regions are not all imiformly distributed over the whole Atlantic within the limits of their 

 bathymetrical distribution. Some species appear to occur exclusively at the European side of the At- 

 lantic, others only at the American side, while others still are known only from the Southern part of 



4 



the Atlantic. It seems therefore necessary to distinguish three Atlantic deep-sea regions, viz. the 

 European, the East American and West African. Undoubtedly several of the species hitherto known 

 from only one of these regions will prove to be more widely distributed, but on the other hand several 

 of the species are so well known and characteristic that it may be regarded as certain that they can- 



1 A very nearly related species, Eckinometra prisca, is described by Cotteau from the Miocene of Anguilla. (De- 

 scription des Eckinides tertiaires des lies St. Barthelemy et Anguilla. Sv. Vet. Akad. Handl. XIII. 1875.) 



