60 



SEA-SHORE LIFE 



SAND-DOLLAIt. 



When young the spines are banded with dark gray and white, 

 but they become dark brown or dark purple in the adult urchin. 

 The body of the urchin is sprinkled over with glistening blue eyes 



each one of which is jsrovided 



_ with a number of prismatic 



lenses, a retina and nerves. 



The Sand Dollar, (Echi- 

 narachniuaparina. Fig. 32), is 

 found in swarms upon sandy 

 bottoms from New Jersey 

 northward to the Arctic Ocean 

 and the Pacific. It is fiat with 

 a rounded edge, about three 

 inches in diameter, and dense- 

 ly covered with short brown 

 spines. The mouth is at the 

 centre of the under side, 

 while the vent is at the mar- 

 gin. Radiating outward from the centre of the upper side one 

 will see the slightly raised pattern of a five-rayed star, the borders of 

 which are outlined by numerous little pores, through which gill-like 

 organs project upward. The sand dollar is enabled to glide over 

 the bottom through the action of its numerous sucker-like feet. 

 When turned over on its back it is unable to right itself, however, 

 and thousands are cast ashore by ever}' great storm. An indelible 

 ink is prepared from sand dollars by pounding them up in water. 

 The Brittle Sea-Cucumber, fSynapta inhcerens, Fig. 33 J, lives 

 in sand tubes within sandy or muddy beaches from the Carolinas to 

 Cape Cod, and is also found on the coasts of Europe. At first sight 

 it resembles a worm, but it is an Echinoderm closely related to the 

 starfishes and sea urchins. Its body is highly contractile, but when 

 extended is about one-eighth of an inch in diameter and more than 

 a foot long The creature is translucent with five white lines 

 marking the places where muscle bands extend down the body. The 

 skin is covered with little white dots that indicate the places occupied 

 by minute calcareous anchors which enable the animal to obtain a 

 hold when moving. The mouth is at the front end of the long worm- 

 like body and is surrounded by twelve feathered tentacles. The coiled 



