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. 



Pi. 212. Under- surface of Star-fish (Ooniaster reticulatus), showing ambulacral 

 grooves and protruded suckers. 



About one hundred and fifty species are known. These 

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

 rows of feet, represented by the common five -fingered 

 Asterias; or having two rows of feet, as the many-rayed 

 Sola8ter,QT " Sun -star," and the pentagonal Goniaster ; 

 (2) species having long, slender arms, which are not pro- 

 longations 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 



