ECHINOIDEA 



305 



Biscay and the Azores. The bathymetrical distribution is 700- 

 3120 m. 



Fig. 173. — Echinus Alexandri ; naked test, from above. Nat. size. 



7. Echinus affinis Mrtsn. (Fig. 174.) 



Test low, but rounded or subcorneal, not flattened above. 

 The primary- tubercles of the interambulacra form regular, 

 prominent series, while those of 

 the ambulacra are remarkably 

 unequal, either so that the two 

 series in each ambulacrum are 

 regular, but of unequal size, or 

 so that suddenly some of the 

 tubercles, especially at the am- 

 bitus, become much larger than 

 the others. Secondary tubercles 

 on upper side few and small. 

 Primary spines fairly long and 

 slender. No spines on the buccal 

 plates. Globiferous pedicellariae 

 generally with 2 lateral teeth on 

 each side of the blade. The tridentate pedicellariae (Fig. 107, 5) 

 with very slender valves. They reach a size of up to 2-2 mm. 



Fig. 174. — Echinus ajfinis; naked 

 test, from above. Nat. size. 



