64 



Animal Life by the Sea-shore. 



coast, but small specimens are not infrequenti}' found in 

 rock-pools, while the more or less damaged tests of adults 

 may be picked up on the shore. 



The Heart-urchin, Echinocaniuiin cordaliim (Fig. 77), derives 

 its name from the heart-shaped test , whicli has acquired a bilateral 

 symmetry, in accordance with \\'hich botli mouth and ^'ent 

 have shifted their position as compared to that of tj^pical 

 urchins. The former is on the li.iwer surface near the broad 

 end, the latter almost at the very extremity of tlie other end. 

 The test is covered with spines of a yellowish colour, harmonising 

 with the sand, more flexible than in other urcliins, and more 

 hair-like. The Heart- 

 urchin burrows deep 

 in the sand, at some 

 distance from the 

 shore, and, like the 

 Lug-worm , subsists 

 on the small organic 

 particles extracted 

 Irom the sand as it 

 passes through the 



Althougli not 

 often met with close 

 to tlie sill ire, the 

 Sea-Cucumbers, e.g., 

 Ciicunuiria and Holo- 

 Ihuria. must be men- 

 tioned liere in order 

 to call attention to 

 a tj'pe of Ecliino- 

 derms departing very 

 strikingh' from the 

 normal. These 

 creatures, belonging 

 to the group called Holotliurians, arc almost vermiform in shape, 

 the body being elongate and nearh' naked (Fig. 7S) . JMoutli and 

 \'ent open at botli ends of the body, and the former is surrounded 

 bv a cri'wn of branched tentacles, perhaps respiratory in 

 function. The systematic i)osition of Cucittimrui is revealed 

 by the characteristic tubular feet, arra.nged in fi^'e double 

 rows equidistant from one anotlier and running in more or 

 less regidar series parallel to the length of the cylindrical body. 

 Ciiciiiiuin'd pcn/iicfcs grows to a length of six inches; in 



no. 77. HE,\RT-URCHIN. 



{Echinocaydliiu! conf'rli(t)i.) 



