62 



Z00L0G7. 



of the eastern coast of the United States, ISTorthern Europe, 

 and the Arctic Seas. It is common among rocks, ranging 

 from low-water mark to fifty or more fathoms. It eats sea- 

 weeds, and is also a scaven- 

 ger, feeding on dead fish, 

 etc. We have observed great 

 niimbers of them assembled 

 in large groups, feeding on 

 fish ofl:al, a few fathoms be- 

 low the surface, in a harbor 

 on the coast of Labrador, 

 where fishing vessels were 

 anchored. 



On placing an Echinus in 

 sea-water the movements of 

 the animal, especially its 

 mode of drawing itself along 

 by its numerous long tentacles, and how it covers itself by 

 drawing together bits of sea-weed and gravel, may be ob- 

 served. It has button-shaped organs of smell and taste. 



The shell consists of five double rows of limestone pieces 

 called ambiilacral plates, which are perforated for the exit 

 of the tentacles or feet, which are like those of star-fish. 

 There are also five double rows of inter cmibulaoral plates, 

 to which the spines are attached. The sand-cake urchin 

 (Fig. 70) is very flat, with minute spines. 



Fig. 70. — Echmarachnius parmu, com- 

 mon Sand-cake. Natural size. 



Class IV. — Holothuroidea {Sea-citmmbers, Trepang). 



General Characters of Holothurians. — We now come to 

 Echinoderms in which the body is usually long, cylindri- 

 cal, with a tendency to become worm-like. The skin is 

 not solid, and is muscular. Around the mouth are situated 

 the ten branched gills, while the feet are arranged in five 

 rows along the body. 



The trepang or beche-lo-mor (Holnfltuvia edulis) is col- 

 lected in the Moluccas and Australian seas, and when dried 



