SEA-URCHINS, STARFISH, AND BRITTLE-STARS. 149 



NOTE ON DISTRIBUTION. 



Generally speaking, the North Sea is poor in Echinoderms as 

 compared with other parts of our area, bub this is to some extent 

 compensated for by the great abundance of certain common species 

 on its shores. Thus, the common sun-star, Henricia sanguinolenta, 

 and the common starfish (Asterias rubens) are probably commoner 

 between tide-marks on the North-east Coast than on the South and 

 West. On parts of the South and West Coasts the spiny starfish 

 (Asterias glacialis) is to be found not uncommonly between tide-marks. 

 The brittle-stars mentioned are common everywhere, but on the South 

 the handsome yellow Ophiocoma nigra may also be expected between 

 tide-marks. In regard to the sea-urchins, those mentioned in the 

 text are widely distributed, but so far as my experience goes, Echinus 

 miliaris reaches a much larger size between tide-marks on the West 

 Coast than on the East. On the South and West sea-cucumbers are 

 much more likely to be found between tide-marks than on the East. 

 In addition to Cucumaria ladea, other species, such as G. pentades, 

 occur there. 



