54 STAR-F/SIIES AND SEA-URCHINS. 



which the arms are very spreading, being divided into 

 branches and tendrils, as it were, that extend in every 

 direction, but yet bear the same relation to the centre 

 as the rays in the one with which you are familiar ; 

 others in which the arms are united for a part of their 

 length, so that the compact centre is larger ; others in 

 which there are ten arms instead of five, and so on. I 

 will not tire you with the details of all these varieties, 

 because, however their appearance may differ, the 

 structure of one explains, in a general way, the struct- 

 ure of all. 



I should, however, mention one group of these star-like 

 animals, the Ophiitrans, as naturalists call them, 

 because they differ in many features from the other Star- 

 Fishes. On the next page is a picture of one (No. 41).* 

 You see that his build is very unlike that of the Star-Fishes 

 you have seen. The centre is more distinct, and the 

 arms start from it abruptly instead of spreading gradually 

 outward. The locomotive appendages of the Ophiurcuit 

 differ slightly in structure from the suckers of the ordi- 

 nary Star- Fish, and so also does their fashion of moving. 

 Extending one of the arms in the direction in which 

 they mean to go, they then bring forward two others to 

 meet them ; and having thus advanced three arms, they 

 drag the rest of the body on. They are not as easily 

 found as the common Star- Fish, because they are very 

 shy, hiding in crevices of the rocks, and shrinking 

 from any approach however gentle. They are of 

 various colors, yellow, purple, or red, and are very 

 brilliant on the back-ground of dark sea-weed, where 

 ihey are commonly found. 



* Sea-Side Studies (A. Agassiz) 



