236 



THE VOYAGE OF H.M.S. CHALLENGER. 



The preceding table gives us the range of a group of species of which, while many of 

 them extend towards the littoral area, the upper limit is usually near the 100 fathom line, 

 and we find here a proportionally larger number of species extending into deep water, into 

 the next bathymetrical subdivision, than in the littoral species. The usual limit of the 

 continental species in depth is from 350 to 450 fathoms. There are forty-six continental 

 species of which ten extend to great depths. The species which have an exceptionally 

 great bathymetrical range are — Salenia hasiigera and Salenia varispina, Ccelopleurus 

 Jloridamcs, Aspidodiadema tonsum, Phormosoma sigsbei. Echinus elegans. Echinus norve- 

 gicus, ScUzaster fragilis, Schizaster moseleyi, and Schizaster orhignyanus. 



The continental species are distributed as follows, excepting, of course, the few species 

 which extend beyond the usual littoral limit downwards, and the species of this group 

 which reach upwards from the abyssal district, and thus produce a bathymetrical mixture 

 similar to the mixture we might obtain of successive geological horizons : — 



EcHmoTHURiD.-E (6 species). 



Asthenosoma, 5. 

 Phormosoma, 1. 



CiDAEiD.E (4 species). 

 Dorocidaris, 2. 

 Porocidaris, 1. 

 Goniocidaris, 1. 



Salenid^e (4 species). 

 Salenia, 4. 



ARBACiADiE (3 species). 

 Podocidaris, 1. 

 Coelopleunis, 2. 



DiADEMATiD.E (3 species). 

 Aspidodiadema, 2. 

 Micropyga, 1. 



Or twenty-nine species of Desmosticha distributed among fourteen genera. The 

 Clypeastridse have entirely disappeared. 



Among the Petalosticha there are seventeen species distributed among the following 

 fifteen genera. 



Temnopleurid^ (2 species). 



Temnechinus, 1. 

 Trigonocidaris, 1. 



TRiPLECHiNiDiE (7 species). 



Hemipedina, 1. 

 Echinus, 6. 



NucLEOLiD^ (3. species). 



Neolampas, 1. 



Conochipus,'!. 



Catopygus, 1. 

 Ananchytid^ (3 species). 



PalcBOtropus, 1. 



Zdnopneustes, 1. 



Paleopneustes, 1. 



Spatakgina (3 species). 



Spatangus, 1. 

 Nacopatagus, I. 

 Echinocardium, 1 . 



