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 (Gronicuster reticulatus ), showing ambulncral 
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 Solaster, 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 
