SEA-URCHINS, STARFISH, AND BRITTLE-STARS. 



147 



KEY FOR THE IDENTIFICATION OF THE SPECIES 

 DESCRIBED IN THIS CHAPTER. 



Asterias 



ECHINODERMA. 



(1) The Asteroids, or Starfishes. Body star-shaped, with stout 

 arms containing prolongations of the digestive and reproductive organs, 

 and open anibulacral grooves. 



'Spines small, nu- 

 merous, with 

 one row down 

 centre of arms 

 A. nibens. 

 Spines large, not 

 very numerous, 

 arranged in 

 three to five 

 rows A. gla- 

 cialis. 



Anibulacral 

 groove narrow, 

 fringedbydense 

 rows of spines 

 H. sanguino- 

 lenta. 



Rays five, rarely 

 six 



Tube-feet in four v 

 rows, skeleton 

 reticulate, its 

 small plates 

 bearing sim- 

 ple spines. 

 Pedicellarise 

 present 



Tube-feet in two 

 rows, skeleton 

 reticulate, 

 meshes bear- 

 ing clusters of 

 small spines. 

 No pedicel- 

 larice 



Henricia . 



Rays more thanj 



grooves fring- 

 ed by com 

 like spines 



rRays 11 - 14, 

 colour red or 



/Dorsal spines purplish red, 



brush - like, dorsal spines in 



tufts S. pap- 

 Solaster . .1 posus. 



Rays 9-11, colour 

 usually purple, 

 dorsal spines 

 much crowded 

 S. endeca. 



(2) The Ophiuroids, or Brittle-Stars. Body star-shaped, arms long 

 and slender without prolongations of the digestive or reproductive 

 organs ; no distinct anibulacral groove. 



Nomouth-papil-\ 



1, arm spines f Arms fragile and 



notched, ^ G \.0nhiothrix \ long ' s P ines 



with spines f * 'j long and glassy 



and distinct [ 0. fragilis. 

 radials . ./ 



Tooth - papillae 

 (see p. 131) 

 present . 



