260 COMPARATIVE ZOOLOGY. 



water is instant death to them. They have the power of 

 reproducing lost parts to a high degree. They are very 

 voracious, and are the worst enemies of the Oyster. 



FIG. 212. Under - surface of Star-fish (Goniaxtw reticulatut*), showing ainbulacral 

 grooves and protruded suckers. 



About one hundred and fifty species are known. These 

 may be divided into three groups: (1) species having four 

 rows of feet, represented by the common five -fingered 

 Asterias ; (2) species having two rows of feet, as the many- 

 rayed Sofaeter, or " Sun-star," and the pentagonal Goni- 

 aster; (3) species having long, slender arms, which are not 

 prolongations of the body, and are not provided with suck- 

 ers, as the Ophiura, or " Brittle-star," and Astrophyton, or 

 " Basket-fish." The last are of inferior rank, and resemble 



