106 



THREE CRUISES OF THE " BLAKE." 



while the structure of the ambulacral furrow approaches that 

 of the Comatulse. Hymenodiscus and Brisinga thus form 



Fig. 383. — Hymenodiscus Agassizii. 1^5.. (Perrier.) 



among starfishes a very peculiar family, marked by most excep- 

 tional characters. The study of Hymenodiscus, closely allied 



Fig. 385. Magnified spine. 

 Hymenodiscus Agassizii. (Perrier.) 



to the northern Brisinga, has had an important bearing on the 

 morphology of the starfish skeleton. 



