AStERIADyE OF THE IRISH SEA. ] 15 



what species figured by Link is the species named by Lin- 

 naeus. 



What is the cause of this singular confusion ? Simply 

 this ; there has as yet been no attempt made to ascertain 

 the generic and specific value of the various organs and 

 tissues in this class of animals. The zoological value of 

 specific groups among the Echinodermata has also been 

 neglected, most naturalists being content with the division 

 of the great genus of Linnaeus, Asterias (itself an Order), 

 into two genera, Asterias and Ophiura, instead of regard- 

 ing those genera in the light of families, to which rank 

 they are undoubtedly entitled. 



I have alluded to the work of Link, " De Stellis Marinis 

 Liber singularis." In that work, though published so long 

 ago as 1733, there is much clearer perception of the true 

 arrangement of star-fishes than in most of the volumes 

 since published wherein those animals are described. Link 

 makes many genera, but unfortunately, probably in conse- 

 quence of want of opportunities for studying the living 

 animal, based his genera on a false principle, viz. the num- 

 ber of rays, a character scarcely even specific among a large 

 portion of the Asteriae, although of great consequence in 

 the family Ophiura\ Very lately, Professor Agassiz, who 

 elucidates whatever he studies, has made a more successful 

 attempt at the definition of the genera of Asteriadae. I 

 allude to his " Prodromus of a monograph of the Radiata 

 and Echinodermata," published in the " Annales des Sci- 

 ences Naturelles," for May 1837, a translation of which 

 appeared last year in the Annals of Natural History. The 

 genera into which he divides Asterias and Ophiura are 

 most natural, though the characters he assigns to them are 

 insufficient. A minute examination of such British spe- 

 cies as have come under my notice fully bears out his gene- 



h 2 



