ASTERIAS. 55 



Order 1. Elasipoda. 



Well-marked bilateral symmetry. Tul)e feet on 



ventral and papillae on dorsal surface. Deep 



sea only. 

 Order 2. Pedata. 



Ambulacral feet in rows or scattered. (Thyone, 



Cucumaria.) 

 Order 3. Apoda. 



Without tube feet. Worm-like. (Synapta.) 

 Class 5. Crinoidea. 



Temporarily or permanently attached by a 



stalk. With five branching arms radiating 



from a small disk. 

 Order 1. Neo-Crinoidea. 



Characters as above. (Antedon, Pentacrinus.) 



ASTEROIDEA. 



ASTERIAS. (Starfish.) 



Starfishes are rather common along most coasts and are 

 among the worst enemies of oysters. They can generally be 

 most satisfactorily examined on shallow-water mussel-beds or 

 on rocks covered with barnacles. Places where starfish occur 

 should be visited, and the conditions under which they live ex- 

 amined. Determine : 



1. Upon what and how they feed. 



2. What their enemies must be. 



3. How their arms are repaired when injured. Do you find 

 specimens that are growing new tips to injured arms or are such 

 arms apparently replaced? When an arm is injured how must 

 the animal proceed to repair it? 



4. Do specimens ever conceal themselves? See if specimens 

 can be found wdth pieces of grass and weeds covering them. 

 Try picking these pieces off to see if they adhere. 



5. Do the animals have other means of protection? 

 Examine a specimen and notice: 



1. That the surface by which the animal clings, the oral 

 surface, is different from the other, ahoral surface, and that 



