REPORT ON THE ASTEROIDEA. 535 



Family Echinasterid^;, Verrill, 1871 (1867), emend. 



The family Echinasteridse established by Verrill 1 comprised, the genera Echinaster, 

 Acanthaster, Mithrodia, and. Ferdina. In 1875 Perrier 3 added to this group Solaster 

 (including Crossaster), Cribrella, aud Valvasler, and removed the genus Ferdina to the 

 family Linckiidas. In 1878 Viguier 3 maintained the family as thus constituted, but 

 divided the genera into' four " tribus'," the Echinasterinse, Mithodiinse, Valvasterinse, and 

 Solasterinse, the last embracing the genera Solaster and Acanthaster. In 1884 Perrier 4 

 removed Solaster (recognising the independent genera Solaster, Crossaster, and Lophaster), 

 which he. placed in a distinct family Solasteridae, and Mithrodia, which he also ranked in 

 a separate family. With the latter step I am unable to agree, and I have therefore 

 replaced the Mitkrodiinee as a subfamily of Echinasteridse. With this exception I 

 maintain the generic constitution of the family as last amended by Perrier. 



I have added two new genera to the family — Perhnaster, a form allied to Cribrella, 

 and Plectaster, a genus established for the reception of the remarkable species described 

 by Muller and Troschel 5 under the name of Echinaster clecanus, which has since been 

 erroneously referred by Perrier 6 to the genus Solaster. I have recently had the gratifica- 

 tion of identifying the species in some examples sent to the British Museum from Port 

 Jackson and Port Phillip, respecting which Prof. Jeffrey Bell 7 has subsequently published 

 a brief note recording the new occurrence of this interesting type. Plectaster, n. gen., is 

 characterised by the wide-meshed reticulate arrangement of the abactinal plates, which 

 leave enormous papular areas occupied by numerous papulae (fifty or more may be counted 

 in a large mesh, and the surrounding margin of the membrane perforated by the papula 

 is often papillate) ; by the abactinal plates bearing compact groups of short, equal, upright 

 spinelets imbedded in a membranous mass ; by the presence of actinal intermediate and 

 infero-marginal plates (the latter slightly larger) similarly armed with short, equal, 

 upright spinelets invested in a sacculate membranous bag, which in spirit specimens 

 has the appearance of being deeply invaginated or perforated in the centre ; by the 

 armature of the adambulacral plates, consisting of two parallel semicircular series of 

 short, equal, cylindrical spinelets, four or five in each series, standing upright and 

 palisade-like. Plectaster decanus has a remarkable faeies unlike that of any other form 

 with which I am acquainted. 



1 Trans. Conn. Acad. Arts and Sci., 1871 (1867), vol. i. part 2, p. 343. 

 8 R6vis. Stell. Mus., p. 35 (Archives de Zool. exp'er., 1875, t. iv. p. 299). 



3 Archives de Zool. exper., 1878, t. vii. p. 93. 



4 Nouv. Archives Mus. Hist. Nat., 2e S^rie, 1884, t. vi. p. 164. 

 * Archivf. Naturgesch., 1843, Jahrg. is. Bd. i. p. 114. 



6 Nouv. Archives Mus. Hist. Nat., 2e S6rie, 1884, t. vi. p. 78. 



7 Zoologischer Anzeiger, March 1888, Jahrg. si. p. 121. 



