ECHINOIDEA 295 



among the spines. Tridentate pedicellariae rather coarse, with 

 broad, leaf -shaped valves. Colour greenish, both the test and 

 spines, but the point of the spines usually violet. Grows to a size 

 of up to ca. 50 mm. in horizontal diameter. 



The breeding season is essentially in the early summer 

 months, but specimens with ripe genital products may be met 

 with all the time from February to November. The larva has in 

 the I. stage elongate body -rods, with the point somewhat 

 thickened and branched (Fig. 147, 1-2; 148, 1); in the II. 

 stage it has epaulettes at the base of the postoral and postero- 

 dorsal arms, but none at the posterior end of the body. This 

 species can form hybrids with Echinus esculentus. 



Fig. 166. — Psammechinus miliaris ; naked test from above (1) and below (2). 



Nat. size. 



It appears to be rather omnivorous ; according to the bottom 

 on which it lives, its food consists of Zostera, algae, or all sorts of 

 bottom organisms. It is accused of doing damage on the oyster 

 banks off the Thames. 



This species is common all round the British coasts ; also 

 known from the Rockall Bank. It is essentially a littoral form, 

 living among sea-grass, algae, often found under stones and on 

 rocks within the tide limits. It has been recorded as boring holes 

 in the rocks, like Paracentrotus lividus. It is distributed from the 

 Trondhjem Fjord along the Scandinavian coasts to the Baltic and 

 the North Sea, and from Iceland to Morocco and the Azores, but 

 is not found in the Mediterranean. It does not occur at Greenland 

 or the Atlantic coasts of America. Bathymetrical distribution, 

 0-ca. 100 m. 



