11 THE VOYAGE OF H.M.S. CHALLENGER. 



probable that a greater number of starfishes were obtained than are here recorded ; those 

 enumerated, however, appear to be all the authenticated examples now preserved.) 



In the " Knight Errant " collection are 9 genera, 1 subgenus, 10 species, and 2 

 varieties ; of which 4 genera, 2 species, and 2 varieties are new (two of the new genera 

 being based on types of which representatives were previously known). 



In the "Triton" collection are 11 genera, 11 species, and 2 varieties; of which 5 

 genera, 4 species, and 1 variety are new, and two of the new genera are established on 

 types of which representatives were previously known. 



In the latest summary of the Asteroidea, published by M. Perrier 1 in 187S, 454 

 species are enumerated, representing 52 genera. Three of the genera, however, included 

 by M. Perrier are invalid or synonymous, the abstraction of which reduces the number 

 recognised by him to 49. Representatives of 38 of these genera were obtaiued by the 

 Challenger ; that is to say, representatives of more than three-fourths of the previously 

 known types. The remaining 11 genera are either extremely rare or of very local 

 occurrence. These figures indicate in a striking; manner that the collection made by the 

 Challenger affords a fair representation of the general character of the Asterid fauna of the 

 globe, so far as known. 



The proportionally large number of new species is not surprising, when it is borne in 

 mind that a considerable portion of the track of the Challenger passed through regions 

 which had hitherto been wholly unexplored, or in which the dredge had never previously 

 been employed. 



The long list of Asterids inhabiting abyssal depths brought to light by the Challenger 

 and the other Expeditions herein discussed may be said to have opened a new chapter in 

 the history of the Asteroidea. The summary of these forms, nearly all of which belong 

 to previously unknown types, given in the Tables appended to the Report affords the 

 most striking evidence of the important contribution made by the Challenger to our 

 knowledge of the group. Reference to these Tables will render any words of comment by 

 me unnecessary here. 



The archaic characters of a number of the deep-sea forms are highly remarkable, and 

 furnish not only a confirmation of the validity of the classification now adopted for the 

 Asteroidea, but also give an important clue to the systematic position of many of the 

 extinct members of the Class. 



The large accession of new forms has greatly extended our knowledge of the morpho- 

 logical plasticity of many types, and has thrown important light on the constitution and 

 relations of groups and families. In all cases the descriptions take cognisance of external 

 and general morphological structure, and are not confined merely to details of specific 

 difference, from the systematist's point of view. 



All the systems of classification previously employed by writers on the Asteroidea are, in 

 1 Nouv. Archives Mus. Hist. Nat., 2e S£rie, t. i. p. 73. 



