5G0 THE VOYAGE OF H.M.S. CHALLENGER. 



laster paheocrystallus ' than to any other species ; it may however be distinguished by its 

 general habit, by the form and character of the pedicellariae, and by the posture and 

 character of the armature of the adambulacral plates. Neither of the three forms above 

 referred to could possibly be mistaken for Pedicellaster scciber. 



Family Asteriid^e, Gray, 1840, emend. 



The investigations of the last decade have resulted in the establishment of more 

 definite morphological limits for this cosmopolitan family than were formerly recognised, 

 and the removal of several genera whose plan of structure is essentially different. 



The genera now classed together in the family Asteriidse constitute a well-defined 

 group, the alliance of which is natural and 'self-evident. They are enumerated in the 

 following table. 



Syno})sis of the Genera included in the Family Asteriidse. 



A. Abactinal skeleton well developed. 



a. Abactinal skeleton reticulate. 



a. Abactinal plates bearing definite spines . . ' . . . . Asterias. 



b. Abactinal plates bearing large spherical tubercles .... Uniophora. 



b. Abactinal skeleton composed of broad imbricating plates, covered with thick 



membrane masking the plates and their appendages .... Calvasterias. 



B. Abactinal skeleton more or less aborted. 



a. Rays five. Form subpentagonal . Anasterias. 



b. Rays numerous and elongate Pyawpodia. 



Genus Asterias, Linne. 



Asterias (pars), Linne, Systema Naturae, 1766, ed. xii. p. 1098. 



Stellonia (i)ars), Nardo, De Asteriis, Oken's Isis, 1834, p. 716. 



Uraster (Agassiz), Forbes, Mem. Wern. Soc. 1839, vol. viii. p. 114. 



Asteracanthion (pars), Miiller and Troschel, Monatsb. d. k. preuss. Akad. d. Wiss. Berlin, April 1840, 



p. 102. 

 Leptasterias, Verrill, Proc. Boston Soc. Nat. Hist., 1866, vol. x. p. 350. 

 Coscinasterias, Verrill, Trans. Conn. Acad. Arts and Sci., 1871 (1867), vol. i. part 2, p. 248. 

 Manjaraster, Hutton, Cat. Echin. New Zealand, 1872, p. 4 (non Margaraster, Gray). 

 Marthrtsterias, Jullien, Bull. Soc. Zool. France, 1878, p. 141. 



1 Doubt has been expressed by Drs. Danielssen and Koren (Nyt Mag./. Natarvidensk., Bd. xxvii. p. 270 ; 

 Den Norske Nordhavs-Expedition, 1S76-1878, Zoologi, xi. Asteroidea, Christiania, 1834, p. 39) as to the validity 

 of this species, which they consider to be identical with Pedicellaster typieus. The arguments drawn from certain 

 points of structure, which they state were insufficiently described by Sars, strongly support that view ; never- 

 theless, whilst acknowledging the cogency of the facts adduced by my learned colleagues and with full respect 

 for their judgment, I venture to retain the species, at least for the present, as, after the examination of further 

 specimens referred to Pedicellaster typieus, I am still inclined to believe that the two forms are distinct. I 

 hope, on a future occasion, to be able to compare them side by side and finally settle the question. 



