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 (Goniaster reticulatus), showing amhulacral 
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 
Solaster, or “ 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 Astropfiyton, or 
“ Basket-fish.” The last are of inferior rank, and resemble 
