i88 



ECHINOIDEA. II. 



preseiice of tliese species and tlie absence of several remarkable American forms then really seems 

 to mark tliis part of the Atlantic deep-sea as a separate region, distinct from tlie American deep-sea 

 region. It is also worth noticing that the P/iormosoina placenta of this region appears to be somewhat 

 different from the American form (the Var. Sigsbci). 



The West African Atlantic deep-sea region comprises the tract from the Azores to about 

 St. Helena. With the exception of the sea off the Azores it is very imperfectly known, and the whole 

 «region > will perhaps prove to be untenable, tliongh it now a^jpears to have several species peculiar 

 to it. — The following species are known from this region: 



Dorocidaris papillata 



— nnda 



Porocidaris pnrpurata 

 Phormosoma placenta 

 Hygrosoma Petersi 

 Sperosoma Grimaldi 

 Dermatodiadema antillarum 

 Salenia hastigera 

 Trigonocidaris albida 



Aceste bellidifera 

 Palæotropns Hirondellei 

 Peripatagns cinctns 

 Homolampas fragilis 

 Hemiaster expergitus 

 Spatangns purpureus 



— Raschi 



Brissns Damesi 

 Brissopsis atlantica(?) 



Genocidaris macnlata 

 Echinns atlanticus 



— Alexandri 



— affinis 

 Echinocyamns pusillus 



— grandiporus 



— macrostomus 

 Calymne relicta 

 Cj'stechinus clypeatus 



Of these the following species are known from this region only: Dorocidaris nuda (also littoral), 

 Echiniis a/lanficHs, Echinocyamns vmcrostouuis, Calyinnc relicta, Cystccliinus clypcatas, Palæotropns Hi- 

 rondellei and Pcripatagus ciiictus. Probably, however, several of these species will prove to have a 

 considerably wider geographical range, and this region upon the whole is very problematic; especially 

 it might be more natural to include the Sea off the Azores in the European atlantic region. 



The East American Atlantic deep-sea region comprises the whole western half of the At- 

 lantic, from the Davis Strait to at least off La Plata, and perliaps even farther southwards. Also the 

 Caribbean Sea and the Mexican Gulf belong to this region. It is, of course, not sharply limited from 

 the East American littoral region, several species ranging from the littoral to the abyssal zone. 



No less than 74 species are known to occur in this region, which is thns by far the richest of 

 all the Atlantic regions. These species are: 



Dorocidaris papillata H)-grosoma Petersi 



Tromikosoma Koehleri 

 Aspidodiadema Jacobyi 

 — tonsum 



Dermatodiadema antillarum 

 Diadema antillarum 

 Hemipedina cubensis 

 Arbacia j^unctulata 

 Podocidaris scutata 

 — sculpta 



Coelopleurus floridanus 



— abyssicola 



— Blakei 



— micans 

 Cidaris affinis 



— tribuloides 

 Tretocidaris Bartletti 

 Stereocidaris ingolfiana 

 Histocidaris Sharreri 

 Phormosoma placenta 



var. Sigsbei 

 Calveria hystrix 

 Aræosoma fenestratum 

 - Belli 



Salenia goesiana 



— Pattersoni 



— varispina 



Salenia hastigera 

 Trigonocidaris albida 

 Genocidaris maculata 

 Echinns elegaus 



— gracilis 



— Alexandri 



— affinis 

 Strongylocentrotus drobachiensis 

 Psammechinus variegatus 

 Tripneustes esculentus 

 Echinometra lucunter 

 Pygastrides relictus 

 Echinocyamns grandiporus 

 Clypeaster latissimus 



